Friday, October 31, 2014

Salinity and Agriculture

Salinity is an important factor when planning to grow crops in an agricultural land or when attempting to reclaim desert land in Egypt for agricultural purposes. We consider water salinity and salinity of soil. Some plants withstand salinity more than others. For instance olive trees can withstand high rates of salinity in water and soil. Date palm trees can also withstand high rates of salinity in water and soil. Many other crops and trees cannot stand high rates of salinity. Salinity is measures in parts in a million. So, a water source that has a rate of salinity of 1000 ppm means that for every million parts of water there exists 1000 parts of salt.

A common problem that arises when attempting to reclaim desert land for agricultural purposes is the surfacing of too much salt on the topsoil. When this happens, the soil becomes ruined and agriculture cannot resume there.

Thursday, October 30, 2014

Farmland Soil

Farmland Soil

When looking for agricultural land or desert land to reclaim in Egypt the first two things to check are salinity in water and soil. Additional soil tests should be done to determine pH value as well as presence (or absence) of minerals.

Conditions present in a specific area of land can determine which plants can grow in it naturally. It also helps realize which weeds can thrive there. All this helps when attempting to do permaculture.

It is crucial to measure pH value of a soil to know which plants can grow in it and to modify the pH value if necessary in order to accommodate for the needs of plants you would like to grow. The herb spiral might offer a continuum of different humidity levels as well as light intensities and pH values.

This might give a clue why the type of weeds that grow in a specific soil actually 'fix' that soil and improve it by balancing it out through making it more or less acidic, more or less compact and more or less saline.

Making Pollution Disappear

It is interesting to note that there are organisms, specially microorganisms, that can tolerate living in some extreme conditions of temperature, humidity, salinity or acidity and alkalinity. Some also can tolerate high concentrations of 'toxic' materials such as heavy metals. It would be nice to see if such organisms can help in reducing pollution from such pollutants.

Wednesday, October 29, 2014

Microclimate

Indirect Effecting

The concept of an organism relying on other organisms and those other organisms being affected by factors such as the temperature thus consequently affecting the first organisms is an interesting one. This arrangement can help us look at communities of people in society where the presence of some types of people depends on the presence of other types of people. We can affect the presence of the first type of people by changing factors that affect the second type of people and thus indirectly affecting the first type.

Environment May Reverse Competition

The outcome of competition between tow organisms can be in favor of one of them within specific conditions and in favor of the other within different conditions (such as different temperatures). Similarly, we can find that the competition between humans in society (businesses or individuals) can be in favor of one side rather than the other according to the conditions of the environment.

Ecology and Growing Plants

The science of ecology can help a lot in determining how communities of plants can live together and interact with each other and with the environment around them and its factors. It is interesting to know all about factors affecting plants such as humidity, temperature, pH value, salinity and the presence (or absence) of specific minerals.

Humidity Loving Insects

I was surprised to find the humidity loving insects in the soil with my balcony plants while not having watered the plants for quite a while. I later came to the conclusion that probably the shade created by the small growing tree and the mulch and good compost based soil have all collaborated to keep the soil under the mulch highly humid. It's the concept of microclimates again.

Microclimate

The idea of microclimates provides a lot of hope for city dwellers. Urban settings have long suffered from high rates of air pollution and increased temperatures due to the heat island effect. This has been 'remedied' using technology in the form of electric air conditioners which actually worsen the local environmental temperature by creating more heat, not to mention consuming a lot of energy. People thus go into a vicious circle.

Microclimates, however, provide us with hope. One can still create a microclimate around his own home or neighborhood by growing more trees and using a number of natural shading and cooling techniques.

Composting Worms

Ecology can help a lot in keeping composting worms and earth worms. The science of ecology can provide us with the knowledge to create successful worm farms.

Tuesday, October 28, 2014

Road Wild Plants

It would be interesting to monitor wild plants that show up on the sides of desert roads in Egypt. They appear in very interesting patterns as if they had been planted deliberately. Their spacing and distribution is striking. It would be interesting to see their dispersion patterns, when do they grow and when do they die out and in which locations they are distributed. It would be nice to see how they get water, is it from the sparse rain or from the humidity caused by human activity or from other sources or a combination of sources and factors. It would also be interesting to check out their species and how such species are distributed and if there exists communities and if there are animals or other organisms that form communities with them.

Do

Take photos of wild plants dispersed on the sides of roads in Egypt.

Temperature Twins

Could there be such thing as temperature twins? If two organisms thrive in a particular temperature ranges, even though they live in different geographical areas, could there be some relationship between them? That could be an interesting question to research.

Sunday, October 26, 2014

Microclimates

Variation on Earth

The inclination of Earth on its axis while rotating around itself and the sun creates such variation in seasons. The spherical shape of the earth itself lends to interesting variation on earth. The presence of mountains and different altitudes also helps create even more variation on earth.

Variation can be with time or according to geographic location.

Microclimates

Isolation?

The concept of microclimate gives hope. It allows one to think that despite the destruction, pollution and deteriorating environment taking place globally, yet one can still live in a relative paradise and create his own microclimate and niche environment.

That does not mean that we should disconnect from what's going on around us and leave the earth to sink, as we are all connected and will get affected at the end no matter how 'isolated' we might be. It just means that in parallel with trying to "save the earth" we can still live in relative bliss by enjoying our own blessed microclimates in which we can thrive. Just planning some trees around your home can help you go that direction.

That's why an urban setting where trees are grown can be up to 10 degrees Celsius less in temperature than an adjacent one that has no trees.

Inspiration

The concept of microclimates also provides variation. It provides inspiration that in analogy to microclimates we can find people in urban communities who are living different states of life. The variation in such human communities can be great in a similar way that microclimates create variation. For instance, in a poor neighborhood there could exist some rich people. In an area where disease is rampant there could exist some health people. At a place where ethics have subsides there could exist ethical people. If such variation is lost, ecosystems become fragile and can fail, be destroyed and become replaced with other new ecosystems that allow for more variation and are more resilient.

This variation can perhaps explain the presence of fruits growing out of seasons for Mariam.

Permaculture

The concept of microclimates and variation in small areas can also be used in permaculture to provide for a variety of food in a small area of land.

So, we can find interesting variation, for instance, within Siwa itself at some scattered pieces of land that have springs.

Sea Moderates Temperature

Water from the sea absorbs a lot of heat in contrast to land which absorbs less heat. The land heats and cools very fast compared to the sea. Hence in Alexandria (Egypt) and other coastal cities weather is moderated by the waters in the sea. It can be warm at night and cool during the day.

Manmade Variation

Besides variation created by natural factors, human activity can also lead to a great deal of variation. For instance, during the Eid vacation where a large number of people who are working and living in Cairo (Egypt) go back to their governorates and industry ceases, a great positive variation in the local climates of Cairo shows up. Air pollution rates drop down sharply and the atmosphere becomes much more healthy. I have noticed during the last Eid vacation that birds increased and I believe I've even witnessed a species of bird that I had not been seeing around, it had a pleasant sound that I had not been familiar with earlier. As soon as the Eid vacation came to an end, such pleasant increased variation in species sadly subsided once again.

Saturday, October 25, 2014

Chill to Bloom

Chill to Bloom

Some trees need a period of chilling, such as apples and pears, in order to bear fruit. If the climate in which they are grown does not provide enough chilling (in terms of low temperature and period of time that such low temperature sustains) the tree will not bear fruit. That is why some trees would not be successful in warmer areas that do not provide such low temperatures. That's why also some trees would fail in bearing fruit if the winter of some year does not prove cold enough. This takes place more in temperate climates where winter is not always as cold as desired by such trees. Every type of those trees has its own chilling requirements.

Seed Germination

We sometimes put the seeds of some trees in the fridge in order to enable them break out of their state of seed dormancy. This occurs naturally in nature when seeds are exposed to cold climate followed by a period of warmth.

Friday, October 24, 2014

Sunstroke

Egypt

I am eager to know more about life at high temperatures as this is suitable for Egypt. I'd like to know how plants deal with that and how humans and other organisms deal with it too.

Four O'Clock Flowers

I have noticed that my four o'clock flower plants have acclimatized with high temperature when the tree that used to shade them was pruned and they suddenly received a higher doze of sunlight than they were used to. During the following season they managed to tolerate the heat much better. I believe the mulching I have added to them helped make them tolerate the extra heat yet I believe their ability to acclimatize did have a profound effect as well.

Sunstroke

Humans also can get a sunstroke if they are exposed to excessive heat, through strong direct sunlight, for an extended period of time (a number of hours). This shows how the body fails to deal with the excessive heat and how its cooling system has a limit after which it can break down. Of course keeping hydrated by drinking lots of water helps in avoiding such sunstrokes and can also help in relieving the effects of a sunstroke after it hits.

That's why when running they advise us to drink lots of water before, during and after the run itself. That's why I get really tired and loose energy after such a running day in the sun particularly if I do not consume enough water.

Human Cells

I remember at school that in biology I heard that cells of human tissue would solidify at temperatures above 50 degrees Celsius. This fact was pretty interesting for me, as for me intuitively things liquify at higher temperatures rather than solidify. The teacher explained it by making an analogy with the white of an egg, it solidifies when heated. This notion was scary to me, as it signaled the death of human tissue at such high temperature. I wounder if this piece of info was really true. I would like to check it out and know more about how this process works and consequences and all.

Sinai

I wonder what interesting wild plants would be found in Sinai that withstand such high desert heat and low availability of water.

Fire-free Egypt

In Egypt we do not usually have high risks of fire despite the high temperatures and also low humidity. The reason behind this is mainly that we do not have forests in Egypt. Houses also are almost never built using wood (perhaps also due to the lack of presence of forests in Egypt).

Fire-surviving Plants

It is interesting to realized that some plants would not regenerate or propagate (seeds would not sprout) except after experiencing very high temperatures of a fire.

Sterilization

That's why we use very high temperatures to sterilize something. Such high temperatures can kill harmful microorganisms.

Solarization

This also explains the concept of soil solarization that is sometimes used in agriculture to sterilize soil from 'harmful' microorganisms.

Also water solarization is a method by which water can be purified by exposing it to direct sunlight for a specific period of time.

I have also heard before that direct sunlight as it falls for a period of time on streams of water can break down pathogens and help purify the water.

Compost

That's why compost heaps that are high enough can reach high temperatures that would kill pathogens. Compost heaps higher than a certain level though might even cause a fire! It is therefore advisable to keep compost heaps at a height of 1 meters only and not more.

Biomimicry in Houses

It would be interesting to look at the many strategies that organisms employ to avoid, reduce or withstand heat in order to get inspiration for methods by which we could build houses for humans that would employ similar natural strategies.

Hell Fire

Hell and fire are considered to be punishment for (bad) humans in Islam, Christianity and other religions. Hell fire represents extremes of heat conditions that the human body is naturally unable to tolerate causing extreme degrees of stress, discomfort and pain.

Edges

When two different environments meet, their interaction creates a continuum of transitioning environments between them which in turn results in a high diversity of organisms living in such high variety of micro-environments. This is basically the concept of edges pointed to in permaculture.

Thursday, October 23, 2014

Genetic Variation and the Evolution of Cold Tolerance

Thoughts

  • Different people have different heat and cold tolerance (that's why). Genetics plus acclimatization.
  • Should therefore fetch plants with genetically good (cold) tolerance plus let them acclimatize.
  • Explains acclimatization for houseplants. (hardening?)
  • Tomatoe varieties that can withstand cold temperature (and be grown in winter) in Egypt.
  • That's why plants I have have acclimatized to the weather (heat) and water (low).
  • That's why it's best to take cuttings or seeds from plants that grow nearby in your same area (for instance for me: from Nasr City rather than from Giza).
  • I love graphs that show results of experiments (data plotted)!
  • Under a certin temperature, a plant or organism stops attempting to acclimatize.

Do

  • Should go explore wild plants in South Sinai and in Siwa (Dr. Mahdy).

Textbook

  • Aclimatization vs genetic factors.
  • "Cold tolerance varies between geographic races of a species."
  • Opuntia fragilis (cactus)
  • "The geographic range of crop species has been extended into colder regions by palnt breeders."
  • Umbilicus rupestris
  • "Past climatic changes, for example ice ages, will have changed the temperature tolerance of species as well as forcing their migration."

Life at Low Temperatures

Ideas

Thoughts

  1. Antifreeze in cars, any resemblance with ecology?
  2. Europe and the US feel the cold, for us in Africa we feel the heat is the problem (for their plants too).

That's Why

  1. That's why the human body gets used to AC.
  2. That's why emotional 'hibernation' can help a person withstand and tolerate strong emotional and psychological shock.

Digest

  • "More than 80% of earth’s biosphere is permanently cold."
  • "Cold is the fiercest and most widespread enemy of life on earth."
  • Temperatures below the optimum are harmful, but there is a wide range of such temperatures that cause no physical damage and over which any effects are fully reversible.
  • Damage at low temperatures that can be lethal:
    • chilling
    • freezing
  • Chilling injury: "Many organisms are damaged by exposure to temperatures that are low but above freezing point"
    • "The fruits of the banana blacken and rot after exposure to chilling temperatures."
  • "Temperatures below 0°C can have lethal physical and chemical consequences even though ice may not be formed."
  • "Water may supercool to temperatures at least as low as −40°C.
  • "Organisms have at least two different metabolic strategies that allow survival through the low temperatures of winter"
    • "A freeze-avoiding strategy uses low-molecular-weight polyhydric alcohols (polyols, such as glycerol) that depress both the freezing and the supercooling point and also ‘thermal hysteresis’ proteins that prevent ice nuclei from forming"
    • "A contrasting ‘freeze-tolerant’ strategy, which also involves the formation of polyols, encourages the formation of extracellular ice, but protects the cell membranes from damage when water is withdrawn from the cells."
  • "The tolerances of organisms to low temperatures are not fixed but are preconditioned by the experience of temperatures in their recent past."
    • acclimation: when it occurs in the laboratory
    • acclimatization: when it occurs naturally
  • "The exposure of an individual for several days to a relatively low temperature can shift its whole temperature response downwards along the temperature scale. Similarly, exposure to a high temperature can shift the temperature response upwards."
  • "Acclimatization may start as the weather becomes colder in the fall, stimulating the conversion of almost the entire glycogen reserve of animals into polyols, but this can be an energetically costly affair: about 16% of the carbohydrate reserve may be consumed in the conversion of the glycogen reserves to polyols."
  • "Dormant stages are typically dehydrated, metabolically slow and tolerant of extremes of temperature."

Questions

  1. What's the difference between acclimation and acclimatization?
  2. How do organisms respond to and survive in cold temperatures?
  3. How can plants be acclimated to cold temperature (tomatoes)?

Tuesday, October 21, 2014

Ectotherms and endotherms

Ideas

Thoughts

  1. Analogy: endotherms consume more energy (food) than ectotherms; similarly, houses with AC consume more energy than those using external factors (wind, angle to sun rays, ...) (biomimicry) (high cost vs low cost)
  2. Insulation (cost), also clue for eco-housing

That's Why

  1. That's why pothos variegated leaves show up when there is enough exposure to strong direct sunlight.
  2. That's why you have to stay hydrated when exposed to strong direct sunlight!
  3. That's why we can catch cold when we are exposed to cold temperature for a while.
  4. Hibernation: to escape the cost of endothermy.
  5. Humans have a built-in AC! endotherms (scientifically proven).
  6. Fat insulates heat loss, that's why fat people feel hot!
  7. That's why red cheeks in cold weather.
  8. Shade plants (that's why).

Do

  1. Structure: Interesting, thoughts (do), summary; in paragraph form? (post Is on FB page/blog?
  2. Show diagrams (graphs) in plants course (to explain phenomena) (science).

Digest

  • ectotherms: "rely on external sources of heat."; organisms that have the same body temperature of their environment; they acquire the temperature of the medium in which they live:
    • a parasitic worm in the gut of a mammal
    • a fungal mycelium in the soil
    • a sponge in the sea
  • endotherms: "regulate their temperature by the production of heat within their own bodies"
    • "terrestrial organisms, exposed to the sun and the air, acquire heat directly by absorbing solar radiation or are cooled by the latent heat of evaporation of water"
    • "the reflective, shiny or silvery leaves of many desert plants reflect radiation that might otherwise heat the leaves"
    • "a lizard chooses to warm itself by basking on a hot sunlit rock or escapes from the heat by finding shade"
    • insects: "bumblebees raise their body temperature by shivering their flight muscles"
    • "birds and mammals use metabolic heat almost all of the time to maintain an almost perfectly constant body temperature"
  • Heat loss in endotherms is moderated by:
    • insulation in the form of
      • fur
      • feathers
      • fat
    • controlling blood flow near the skin surface
  • Endotherms pay the price of a large expenditure of energy to regulate their temperature. An even larger amount of energy is used outside the organism's thermoneutral zone.
  • "The responses of endotherms and ectotherms to changing temperatures are not so different."
    • Both are at risk of being killed by even short exposures to very low temperatures and by more prolonged exposure to moderately low temperatures
    • Both have an optimal environmental temperature and upper and lower lethal limits
    • There are also costs to both when they live at temperatures that are not optimal.
    • Temperatures only a few degrees higher than the metabolic optimum are liable to be lethal to endotherms as well as ectotherms
  • Ectotherms are not more primitive than endotherms.
  • "Most environments on earth are inhabited by mixed communities of endothermic and ectothermic animals."
  • Contrast
    • endotherms: high cost–high benefit strategy
    • ectotherms: the low cost–low benefit strategy

Questions

  1. What would it be like if humans were ectotherms?
  2. What are the advantages of ectotherms and the advantages of endotherms?
  3. Why are there ectotherms and endotherms, why not just one type?

Metabolism, growth, development and size

Ideas

Thoughts

  1. Science can help predict plant growth and production (equations, variables: temperature).
  2. Is that why Africans are tall (the high temperature, leading to a high rate of metabolism)?
  3. That's why in hot climates plants grow fast and forests of lush vegetation exist. (Water? Deserts?)
  4. That's why my plants grew noticeably during hot days.
  5. Prediction is amazing for size and development for plants, in agriculture!

Do

  1. Do experiments in balcony on plants.

Digest

  • How individuals respond to temperature:
    • impaired function and ultimately death at the upper and lower extremes
    • a functional range between the extremes
    • an optimum within the functional range
  • "For each 10°C rise in temperature the rate of biological enzymatic processes doubles, and thus appears as an exponential curve on a plot of rate against temperature."
  • Temperature affects:
    • rates of growth: increases in mass (linear)
    • rates of development: progression through lifecycle stages (linear)
    • final body size
  • Day-degree: number of days to develop X degrees above development threshold
  • Physiological time: a combination of time and temperature required for an organism to develop
  • "Together, the rates of growth and development determine the final size of an organism."
  • "For a given rate of growth, a faster rate of development will lead to smaller final size."
  • Temperature-size rule:
    • Development increases more rapidly with temperature than does growth
    • Thus final size decreases with rising temperature
  • Effects of temperature on growth, development and size has practical importance for prediction.

Question

The effect of temperature on metabolism is quite interesting.

Sunday, October 19, 2014

What do we mean by 'extreme'?

Thoughts

  1. Introducing a new organism diversifies the environment in which it was introduced. This is an interesting concept for permaculture.
  2. Importance of temperature in agriculture.
  3. Extreme: to desert dwellers (Bedouins) the water poverty line set by the UN is outrageously high.
  4. What is the difference between these terms: "organism," "individual" and "species"?
  5. The concept of extremeness is even relative among individual humans (within the same species).
  6. The concrete activity, to sense the environment from a plant's perspective.
  7. The ecologist's ability to 'see' the world from an organisms point-of-view reminds us of design thinking.

Digest

  • "To a cactus there is nothing extreme about the desert conditions in which cacti have evolved."
  • "It is ... dangerous for the ecologist to assume that all other organisms sense the environment in the way we do."
  • "The ecologist should try to gain a worm’s-eye or plant’s-eye view of the environment: to see the world as others see it."

Question

What is extreme for an organism may be normal for another. The idea of extremeness is relative.

Ecological Niches

Ideas

Thoughts

  1. If you want to move people out from a place, make changes to the 'environment' of that place so as to make its properties beyond the tolerable conditions of the 'ecological' niche of those people.
  2. Ecological niche dimensions for agriculture.

Do

  1. I would love to play with the computer modeling of ecological niches.
  2. Niche dimensions for plants.

Digest

  • Ecological niche vs. habitat:
    • A habitat of an organism is the sort of place in which it lives.
    • An ecological niche of an organism is "a summary of the organism’s tolerances and requirements."
    • "Each habitat provides many different niches and with quite different lifestyles."
  • Charles Sutherland Elton, in 1933, was the first to write about ecological niche in its current scientific meaning.
  • Hutchinson, in 1957, proposed the modern concept of niche to address the ways in which tolerances and requirements interact to define conditions and resources needed by a species.
  • Niche dimensions: "The ecological niche of a species [is] the boundaries that limit where it can live, grow and reproduce."
    • One-dimensional: temperature (plants)
    • Two-dimensional: temperature, salinity (sand shrimp)
    • Three-dimensional: temperature, pH, availability of a particular food (aquatic organism)
    • N-dimensional: the real niche of a species must be multidimensional
  • fundamental and the realized niche.
    • the overall potentialities of a species
  • Fundamental vs. realized niches:
    • Fundamental niches: "describes the overall potentialities of a species"
    • Realized niches: "describes the more limited spectrum of conditions and resources that allow it to persist, even in the presence of competitors and predators.

Questions

  1. The concept of ecological niche seems to be cool!
  2. It would be cool to explore what computer modeling has to do with the various dimensions of ecological niches.

Saturday, October 18, 2014

Conditions: Introduction

Ideas

Thoughts

  1. The importance of temperature in determining the comfort level of human life.
  2. Altering conditions purposefully (manmade)
  3. Conditions for plants: agriculture (permaculture)
  4. It is no wonder that laymen and traditional wisdom in Egypt gives a very high value to a person based on his or her fertility.
  5. In plants: conditions: survival, growth, reproduction

Do

Houseplants Course

  1. Optimum conditions for each plant.
  2. Plant course: myths: (list needs)
    1. Sun (too much is bad)
    2. Water (don't over-water, don't soak it in water nor drown it in water)
  3. Look for coursera course about plants.

Digest

  • Understanding the distribution and abundance of a species requires knowledge about:
    • its history
    • resources it requires
    • rates of birth, death and migration
    • interactions with their own and other species
    • effects of environmental conditions
  • Environmental condition: "an abiotic environmental factor that influences the functioning of living organisms."
    • temperature
    • relative humidity
    • pH
    • salinity
    • pollutant concentration
  • "Unlike resources, conditions are not consumed by organisms."
  • For practical reasons, we measure the performance of organisms based on:
    • activity of an enzyme
    • respiration rate of a tissue
    • growth rate of individuals
    • rate of reproduction
  • Conditions gradually affect an organism's ability to:
    • reproduce
    • grow
    • survive
  • Effects of environmental conditions:
    • Extreme conditions are lethal
      • temperature
      • pH
    • The condition is lethal only at high intensities
      • toxins
      • radioactive emissions
      • chemical pollutants
    • The condition is required at low concentrations
  • "Temperature is the single most important condition that affects the lives of organisms."

Question

Why is temperature the most important conditions in the environment of an organism?

Thursday, October 16, 2014

Summary of Chapter 1

Thoughts

  1. Evolution in the Quran, any direct reference to it?
  2. "the fittest yet" and not "the est imaginable" does not make sense statistically with the observations available!
  3. Islands provide best environment for divergence, similarly, an isolated oasis or human community would develop a diversity of complementary skills in its residents (medical, ...)
  4. That's why car parkers sprout out in the city at locations full of higher class people.

Digest

  • "Nothing in biology makes sense, except in the light of evolution."
    • evolutionary adaptation
    • theory of evolution by natural selection
      • "the fittest available"not "the best imaginable"
  • Adaptive variation
    • balance between local adaptation and hybridization
    • Ecotypes
    • Genetic polymorphism
      • ocal specialization
  • Speciation: two or more new species are formed from one original species
    • biospecies
    • islands
    • diverge
  • Species live where they do for reasons that are often accidents of history
    • island patterns
    • movements of land masses
    • climatic changes during the Pleistocene ice ages
    • global warming
    • convergent evolution
    • parallel evolution
  • Biomes
    • terrestrial biomes
    • aquatic biomes
    • life form spectra: ecological communities may be very similar even when taxonomically distinct
  • Communities comprise a diversity of species: Environmental heterogeneity:
    • interactions between predators and prey
    • and parasites and hosts
    • and mutualists
    • and the coexistence of similar species

Questions

  1. What is the binding principle in chapter 1?
  2. What have you learnt so far after studying chapter 1?

Wednesday, October 15, 2014

Coexistence of Similar Species

Thought

Again trying to force in the theory of evolution by finding 'excuses' for the coexistence of similar species, like what was done with presence of different species.

Digest

  • Communities support a variety of species performing apparently rather similar roles
  • Antarctic seals have undergone radiative evolution
    • Weddell seal:
      • feeds primarily on fish
      • has unspecialized dentition
    • Crab-eater seal:
      • feeds almost exclusively on krill
      • its teeth are suited to filtering these from the sea water
    • Ross seal:
      • feeds mainly on pelagic squid
      • has small, sharp teeth 
    • Leopard seal:
      • feeds on a wide variety of foods, including other seals and, in some seasons, penguins
      • has large, cusped, grasping teeth
  • Apparently very similar coexisting species may differ in subtle ways:
    • morphology
    • physiology
    • responses to their environment
    • role they play within the community of which they are part
  • The ecological niches of such species are said to be differentiated from one another
Weddell seal
Weddell seal

Question

I don't buy it, the idea of explaining the evolution of similar species to be a result of granular differences within the same geographical environment.

Tuesday, October 14, 2014

Pairs of Species

Ideas

Thoughts

  1. Environments themselves are heterogeneous, the more so to small scale organisms.
  2. Starting with a 'seed' community at a new location can lead to expanding diversity in such community later on.
  3. Again, the close matches between paired organisms is linked to evolution.
  4. Such mutualism among mutually evolved organisms can inspire a model for developing strong healthy relationships between neighboring nations, neighbors as well as people coexisting in the same community.
  5. Types of mutualism can inspire mutualisms in human communities and in the business and political worlds!

Do

Make website, call it ecological inspirations.

Digest

  • "The existence of one type of organism in an area immediately diversifies it for others."
    • An organism may increase the diversity of its environment by contributing:
      • dung
      • urine
      • dead leaves
      • its dead body
    • Its body may serve as a place in which other species find homes
  • One species may have developed a dependence upon another
    • Relationships between consumers and their foods
    • Relationships between parasites and their hosts
  • mutualisms: mutual dependence among two species (stronger than one side dependence)
    • "The association of nitrogen-fixing bacteria with the roots of leguminous plants"
    • "Extremely precise relationships between insect pollinators and their flowers"
  • Organism-environment vs. organism-organism interactions:
    • When a population has been exposed to variations in the physical factors of the environment a tolerance may evolve. The physical factor cannot itself change or evolve as a result of the evolution of the organisms.
    • Coevolution: When members of two species interact, the change in each produces alterations in the life of the other
Eastern tiger swallowtail
Eastern tiger swallowtail

Question

What makes different yet similar species evolve in the same environment?

Monday, October 13, 2014

Environments are Heterogeneous

Ideas

Thoughts

  1. Science is political? Heterogeneity not homogeneity environments in nature.
  2. I still don't get it, the presence of more than one different 'best' fit organism in a particular environment. How does this not contradict with the theory of evolution?
  3. Heterogeneity in human communities.
  4. The mistake of forcing homogeneity in human communities.
  5. Quran: mustard seed (given as an example of a very small thing).

Do

  1. Documenting species of Ferdaws Garden, as part of the Human Centered Design course.

Digest

  • "Why species that live in the same environment are often profoundly different?"
    • "A plant utilizing sunlight, a fungus living on the plant, a herbivore eating the plant and a parasitic worm living in the herbivore should all coexist in the same community."
  • "There are no homogeneous environments in nature."
  • "What appears to the human observer as a homogeneous environment may, to an organism within it, be a mosaic of the intolerable and the adequate."
    • "To a mustard seed, a grain of soil is a mountain; and to a caterpillar, a single leaf may represent a lifetime’s diet."
    • "A seed lying in the shadow of a leaf may be inhibited in its germination while a seed lying outside that shadow germinates freely."
  • Gradients in an environment can also be:
    • in space: altitude
    • in time
      • rhythmic: daily and seasonal cycles
      • directional: the accumulation of a pollutant in a lake
      • erratic: fires, hailstorms and typhoons
  • "Heterogeneity can alter communities by interrupting what would otherwise be a steady march to an equilibrium state"
Mustard seeds
Mustard seeds

Questions

  1. Why are there no homogeneous environments in nature?
  2. What is the effect of artificially enforcing homogeneous man made environments?
  3. What is the relationship, if any, between homogeneity and diversity?

Sunday, October 12, 2014

The 'Life Form Spectra' of Communities

Ideas

Thought

Reinterpreting verses of the Quran about creation of living organisms in light of the theory of evolution.

Do

Should start reading research papers (refereed to in the book, and on Google Scholar).

Digest

  • Divergence
    • Geographic isolation allows populations to diverge under natural selection.
    • Geographic distributions of species reflects this divergence.
    • All species of lemurs are found only on the island of Madagascar.
  • "Gum trees occur where they do because they evolved there – not because these are the only places where they could survive and prosper."
  • Biomes
    • A map of biomes is not a map of the distribution of species.
    • We recognize different biomes from the types of organisms that live in them.
  • Life forms
    • In 1934, Danish biogeographer Raunkiaer developed the idea of "life forms".
    • "He then used the spectrum of life forms present in different types of vegetation as a means of describing their ecological character."
    • Life forms are defined according to the ways in which buds are protected in different plants.
  • Life forms:
    • phanerophytes: trees exposing their buds high in the air
    • chamaephytes: perennial herbs form cushions in which buds are borne above ground
    • hemicryptophytes: buds are formed at or in the soil surface
    • cryptophytes or geophytes: buds are protected on buried dormant storage organs; These allow the plants to make rapid growth and to flower before they die back to a dormant state.
    • therophytes: "annual plants that depend wholly on dormant seeds to carry their populations through seasons of drought and cold"
  • "Therophytes are the plants of deserts, sand dunes and repeatedly disturbed habitats. They also include the annual weeds of arable lands, gardens and urban wastelands."
  • fauna classification
  • Species present in different geographic locations may belong to the same biome yet be very different taxonomically.
Crocus
Crocus

Questions

  1. How come there are various different species evolving in the same environment?
  2. What's with different species complementing one another in a specific environment?

Saturday, October 11, 2014

Terrestrial Biomes of the Earth

Ideas

Thoughts

  1. Different biomes and permaculture (Permaculture: A Designer's Manual by Bill Mollison, 14 chapters)
  2. Biomes: temperature and precipitation: Quran factors for vegetation: water, wind, ...
  3. Communities: some species attract the presence of others. This concept can be used in achieving goals.
  4. Holzer permaculture: growing things in cold high altitude climate (local climate)
  5. Mosses: peat moss (habitat, conserve?)
  6. Polar desert?
  7. Underground water in Egypt's deserts, for use in agriculture, can ecology give us a clue on how to best use such resource?
  8. Observation: Many things in biomes are a seasonal, transient, in migration due to changing weather.
  9. Inspiring ideas from ecology to effect rich and resilient human communities.
  10. Birding clues from ecology.
  11. Cold desert: Mongolia (Gabi).
  12. Vegetation (sporadic yet patterned) along desert roads in Egypt.
  13. Tropical rainforest: my dream.
  14. 3% concentration of salt in water of oceans.
  15. Plants to treat water in fisheries (permaculture)
  16. Ecology and the Aswan High Dam.
  17. Ecological understanding of presence of roaches around households.

Interesting Facts

  1. Plants germinating only after fire!
  2. Epiphytes: rooted on the damp upper branches!

Digest

  • Biomes: where biogeographers recognize marked differences in the flora and fauna.
  • Biomes grade into one another.
  • Eight terrestrial biomes:
    • distribution
    • relation to annual temperature and precipitation
  • Eight biomes
    • tundra
      • occurs around the Arctic Circle, beyond the tree line
      • permafrost
    • taiga (northern coniferous forest)
      • occupies a broad belt across North America and Eurasia
      • liquid water is unavailable for much of the winter
    • temperate forests
      • range from the mixed conifer and broad-leaved forests of much of North America and northern central Europe to the moist dripping forests of broad-leaved evergreen trees found at the biome’s low latitude limits.
      • there are periods of the year when liquid water is in short supply
    • grassland
      • occupies the drier parts of temperate and tropical regions
      • experience seasonal drought
    • chaparral (maquis)
      • occurs in Mediterranean-type climates
      • mild, wet winters and summer drought
    • desert
      • found in areas that experience extreme water shortage
    • tropical rainforests
      • high solar radiation throughout the year and regular and reliable rainfall
      • is the most productive of the earth’s biomes
    • aquatic biomes
Green tree frog
Green tree frog

Questions

  1. It is interesting to know about the different biomes.
  2. Which biomes are better than others?

Friday, October 10, 2014

Convergents and Parallels

Ideas

Thought

Organisms evolved to complement each other in a working system (therefore there cannot be one single best fit for an environment) they specialize each playing a different complementary role in the system: ex: climbing plants and trees.

Question

Did paradise, that Adam and Eve staying in at first, contain a wide diversity of plants (and animals) or was the variety of species around them relatively limited?

Do

Digest

  • Similarity in form and behavior between organisms living in a similar environment, but belonging to different different branches of the evolutionary tree, illustrates the match between the nature of organisms and their environment.
  • The idea that there is only one perfect organism for every environment is proven wrong by such similarities.
  • Convergent evolution takes place when the phyletic lines are far removed from each other, and when similar roles are played by structures are analogous but not homologous.
  • Many plants use the support of others to climb up to gain access to more light.
  • Analogous structure:
    • Different evolutionary origins, similar in superficial form or function
    • "The ability to climb has evolved in many different families, and quite different organs have become modified into climbing structures: they are analogous structures but not homologous."
    • Analogous plants having structural features that are derived from modifications of quite different organs: leaves, petioles, stems, roots and tendrils.
  • Homologous structure:
    • Derived from an equivalent structure in a common ancestry.
    • "In other plant species the same organ has been modified into quite different structures with quite different roles: they are therefore homologous, although they may not be analogous."
    • Homologous plants having structural features that are derived from modifications of a single organ: the leaf
  • The radiation amongst the placental and marsupial mammals is a classic example of parallel evolution (evolutionary pathways within separate groups that have radiated after they were isolated from each other).
  • Similarities between parallels in both the form of the organisms and their lifestyle is so striking suggesting that the environments of placentals and marsupials provided similar opportunities to which the evolutionary processes of the two groups responded in similar ways.
Cobaea scandens flower
Cobaea scandens

Question

Is it possible that two species would have evolved separately in similar but separate environments to become more or less similar to one another?

Thursday, October 9, 2014

Climatic Changes

Thoughts

  1. Is there any hint of glacial cycles or change of temperature in the Quran?
  2. Figs and olives, mentioned in the Quran, do they have anything special with regards to their evolution?
  3. The general Western view has been that humans have had a negative impact on earth and the environment. The call has been for attempting to reduce or neutralize, if ever possible, the harmful effect humans have on the environment. The Islamic view, as it shows in the Quran, has a different perspective. The Quran sees humans as either destroyers or carers and reformers. Islam advocates the latter. The Islamic view therefore is that humans not only can reduce or neutralize their negative impact on earth and the environment but can, and should, through their actions, enhance and maintain such environment to become even better!
  4. It would be cool if I pay a visit to the tropics! I feel a deep connection to such places.
  5. I should go live and teach (ecology) in Sudan!
  6. I am against the author's view of historic accidents and that plants are not well adapted to their environments.
  7. The lush vegetation that had been present in place of the current deserts in Egypt at the time of Ancient Egyptians, were they a result of climatic cycles? Was their disappearance manmade or natural?
  8. Does the concept of succession, popular in permaculture, have anything to do with the succession of plants and their evolution with time in a particular geographical location?

Digest

  • "Changes in climate have occurred on shorter timescales than the movements of land masses."
  • "Much of what we see in the present distribution of species represents phases in a recovery from past climatic shifts."
  • "Changes in climate during the Pleistocene ice ages ... bear a lot of the responsibility for the present patterns of distribution of plants and animals."
  • Technology for discovering, analyzing and dating biological remains is becoming more sophisticated particularly by the analysis of buried pollen samples.
  • "Techniques for the measurement of oxygen isotopes in ocean cores indicate that there may have been as many as 16 glacial cycles in the Pleistocene, each lasting for about 125,000 years."
  • "Each glacial phase lasted for 50,000 to 100,000 years, with brief intervals of 10,000 to 20,000 years when the temperatures rose close to those we experience today."
  • "During the 20,000 years since the peak of the last glaciation, global temperatures have risen by about 8°C."
  • "The rate at which vegetation has changed ... has been detected by examining pollen records."
  • Sequence of trees invading:
  • Forests expand as glaciers retreat! Forests are still expanding till this day!
  • Impact on much smaller space and time scales takes place when high discharge events (associated with storms or snow melt) result in a very small-scale mosaic of patches.
  • "The stream fauna may rarely achieve an equilibrium between flow disturbances."
  • Similar changes also show up in Asia, Africa and South America.
  • "Particular ‘hot spots’ of species diversity are likely sites of forest refuges during the glacial periods, and sites of increased rates of speciation."
  • "Global warming, maybe 3°C in the next 100 years, is predicted to result from continuing increases in atmospheric carbon dioxide."
  • The extinction of the Picea critchfeldii tree in the Quaternary occurred around 15,000 years ago at a time of especially rapid postglacial warming.
  • "Even more rapid change in the future could result in extinctions of many additional species."
Glacier melting
Glacier melting

Questions

  1. Is the current rise in global temperature really attributed to manmade activities or is it just a natural oscillation of temperature inline with temperature variation cycles like those that have been occurring in the distant past?
  2. What effect has repeated climatic change had in the distant past on species and what role has it played, if any, in their evolution?

Wednesday, October 8, 2014

Movements of Land Masses

Thought

After a deep, and heated, discussion it became clear to me that the theory of evolution of species does not conflict with the verses of the Quran or what Islam teaches.

Digest

  • Movement of continents:
    • The wide dispersion of related species across continents first led biologists to suggest that continents were adjacent to one another in the past and have moved apart later on. This view was advocated early in 1915 by Alfred Wegener.
    • Geologists first resisted such view until geomagnetic measurements confirmed this. "The discovery that the tectonic plates of the earth’s crust move and carry with them the migrating continents, reconciles geologist and biologist."
  • The following large flightless birds are one example of widely distributed yet related organisms:
  • Continents moved apart along millions of years (the past 150 to 10 million years ago).
  • "Changes in temperature in the North Sea over the past 60 million years. During this period there were large changes in sea level that allowed dispersal of both plants and animals between land masses."
  • Gondwanaland is one of the two ancient supercontinents that have split about 150 million years ago.
  • "Molecular techniques make it possible to analyze the time at which the various flightless birds started their evolutionary divergence."
Cassowary
Cassowary

Question

Was the wide dispersion of species really why it was first suggested that currently far away land masses have moved away from one another and were in the past adjacent?

Tuesday, October 7, 2014

Island Patterns

Thoughts

  1. Looking for unique species of plants at remote areas (Siwa, Aswan, Sinai).
  2. White people in South Africa, how about those as 'founder populations'? How about White people in Australia, in North America?
  3. I do not buy the idea that mutations are accidental! I only see it 'polite' way of saying that science has yet to discover the patterns by which mutations happen to serve a non-accidental evolution purpose.
  4. I do not agree that species are not perfectly adapted to their environments. I sense that there is something wrong with that. I believe species are indeed most perfectly adapted to their current natural environments. Or what?
  5. I see the events in history that result in the creation of islands or separation of land are no accident. I see them as natural developments that take place within grand patterns to serve a purpose.
  6. My comments above about refusing the thought of accidents, and imperfection might sound unscientific, yet I believe science might prove them one day. Science, to me, is not and should not be the only source of knowledge and it can be guided and inspired by other sources of knowledge.

Digest

  • Drosophila species (fruit flies): 1500 worldwide, 500 in Hawaiian islands, 100 picture-winged
  • endemic: species found in only one area
  • Dispersion of ancestor species (founder population) into new locations and isolation of such locations (such as isolated islands) allow forces natural selection to evolve them into new species
  • Natural selection is confined to the gene pool of the ancestors save only for occasional rare mutations
  • The lineages through which the Drosophila species have evolved can be traced by analyzing the banding patterns on the chromosomes in the salivary glands of the their larvae
  • The oldest islands have the first ancestors while the newest formed islands have the most recently evolved species
  • Island biotas illustrate that:
    • there is a historical element in the match between organisms and environments
    • there is not just one perfect organism for each type of environment
Drosophila
Drosophila

Questions

  1. How do islands form?
  2. How do species specialize and evolve on an isolated island?

Monday, October 6, 2014

Islands and Speciation

Thoughts

  1. The theory of evolution of species and what Islam and the Quran teach, how can they be reconciled?
  2. In Upper Egypt, people are more isolated then those in the Nile Delta area. What effect, if any, does this have on them?
  3. Taking plant species from such remote islands and reintroducing them elsewhere would be an interesting idea.
  4. Breeding, of animals, taken from elsewhere can be interesting.
  5. 'Specialization' of humans when isolated.
  6. Specialization of coexisting humans.
  7. How and why do populations diverge despite being in the same geographic location?

Digest

  • Galápagos Islands are volcanic islands
    • Location: Isolated in the Pacific Ocean about 1000 km west of Ecuador and 750 km from the island of Cocos, which is itself 500 km from Central America.
    • Description: At more than 500 m above sea level the vegetation is open grassland. Below this is a humid zone of forest that grades into a coastal strip of desert vegetation with some endemic species of prickly pear cactus (Opuntia).
  • Darwin's finches: Fourteen species of finch are found on the islands.
  • Microsatellite: The evolutionary relationships amongst them have been traced by molecular techniques
  • The 14 distinct species of finches differ in shape and feeding habits.
  • Isolation of individual islands within the archipelago has led to the evolution of a series of species each matching its own environment.
Small ground finch (Geospiza fuliginosa)
Small ground finch (Geospiza fuliginosa)

Questions

  1. How do populations specialize despite not being geographically separated?
  2. What islands, other than land surrounded by water, exist? (Oases?)
  3. Let's explore the interesting subject of rare and specialized species in isolated islands and the process by which they evolve!

Sunday, October 5, 2014

What do we Mean by a Species?

Thoughts

  1. Gog and Magog, are they different species from humans?
  2. Therefore, by definition, humans all belong to the same species.
  3. Have Gog and Magog specialized and becomes a different species than humans due to isolation?
  4. What about isolated communities like in Siwa, Nubia and other more isolated ones such as in Islands (belonging to India for instance where contact has been attempted yet unsuccessfully).
  5. Hybridization in American population, what does it lead to.
  6. Inadvertent hybridization of F1 hybrids with other forms of the same species or hybridization among different cultivars of a plant may result in unfavorable results in offspring.
  7. What is a cultivar? (A form of ecotype?)
  8. Isolated communities of humans, like Siwa and Nubia, have imposed cultural rules of not marrying from outside their communities.
  9. Donkeys and horses produce infertile mules when they mate. This fits them perfectly within the definition of being two distinct species (two distinct biospecies).
Hybridization against forces of natural selection
Hybridization against forces of natural selection

Digest

  • Speciation, the forming of distinct species, is a process not a sudden event
  • Hybridization and natural selection are two opposing forces
  • According to the Mayr-Dobzhansky test, two organisms belong to the same biospecies if they could breed together in nature to produce fertile offspring
  • Allopatric speciation vs sympatric speciation
  • Ecological speciation is speciation driven by divergent natural selection in distinct subpopulations according to Dolph Schluter (2001)
  • Stages of speciation (in the most orthodox view of ecological speciation):
    1. Two subpopulations become geographically isolated and natural selection drives genetic adaptation to their local environments
    2. Reproductive isolation (pre-zygotic or post-zygotic) builds up between the two subpopulations
    3. The two subpopulations re-meet in a phase of secondary contact
    4. The hybrids between individuals from the different subpopulations are now of low fitness. Natural selection will then favor any feature in either subpopulation that reinforces reproductive isolation preventing the production of low fitness hybrid offspring. These breeding barriers then cement the distinction between what have now become separate species.
  • In northern Europe, the lesser black-backed gull and the herring gull are now two distinct species. They do not hybridize and are therefore true biospecies.  Their 'ancestors' still hybridize freely after spreading east and west from Siberia.
Lesser black-backed gull and European herring gull
European herring gull (top) and lesser black-backed gull (bottom)

Questions

  1. So, what exactly is a species?
  2. So, ecotypes are different forms of the same species? Also different forms, like peppered moths (melanic and nonmelanic) belong to the same species?
  3. How come species are classified by scientists then reclassified later on in a different way?

Saturday, October 4, 2014

Variation within Species with Manmade Selection Pressures

Thoughts

  • How does manmade influences affect the species of cats, doges, mice, weasels, doves, hoopoe, craws, home sparrows and bats in urban areas in Cairo? (It probably has a lesser effects on birds, since they travel even more easily than the other animals. On the same token, trees must be affected the most, since they are immobile.)
  • Pigeons at Siwa and donkeys at Siwa appeared to be much healthier than those in Cairo. They live amongst nature, feed on a healthy natural diet and live in a healthy environment with no air pollution. (Siwa also is in the North West of Egypt, from wear most of the wind comes, and is located at the lowest place in Egypt, almost, which makes it insusceptible to winds blowing off industrial pollution from anywhere.)
  • It is good (for humans) to live away from the direction of wind that brings airborne industrial pollutants. Helwan is one such area where many suffer health issues due to high pollution caused by the presence of cement factories there.

Digest

  • Local specialization within species (natural selection in action) has sometimes been driven by manmade ecological forces, especially those of environmental pollution.
  • Dark (melanic) forms peppered moth (Biston betularia) increased in industrial polluted areas in the UK
  • Many populations of peppered moths in the UK were polymorphic: melanic and nonmelanic forms coexisted
  • Transient polymorphism:
    • The dark form of moth increase in the UK
    • The fall in the population of dark peppered moths after pollution was reduced is again a from of transient polymorphism
  • Industrial melanism:
    • Definition: Industrial melanims is the phenomenon in which black or blackish forms of species have come to dominate populations in industrial areas
    • In the dark individuals, a dominant gene is typically responsible for producing an excess of the black pigment melanin
  • Birds preying on peppered moth are those causing natural selection to work, they eat the typical (light colored) moths in industrial places while they prey on the dark ones in pollution free places
  • Sulfur dioxide destroyed most of the moss and lichen on tree trunks on which nonmelanic moths rest thus depriving them from their ability to camouflage
  • Transition from coal to oil and electricity in addition to legislation passed to impose smoke free zones and to reduce industrial emissions of sulfur dioxide in Western Europe and the US caused the frequency of melanic forms of peppered moth to falll back to near pre-industrial levels
Melanic and non-melanic peppered moth
Melanic and non-melanic peppered moth

Questions

  1. What manmade factors, other than pollution, can affect selection in species?
  2. How does breeding affect the balance of evolution?
  3. Can manmade interference in any way have a positive effect on populations and communities compared to leaving them without any manmade influence?

Friday, October 3, 2014

Genetic Polymorphism

Thoughts

When selecting a plant from its natural habitat, say from Aswan, to transplant elsewhere, it is a good idea to select from a location that would provide the characteristics you desire in the plant (ex: lower elevation to be more drought tolerant ... etc.)

Digest

  • "The distinction between local ecotypes and polymorphic populations is not always a clear one."
  • Genetic polymorshipsm was defined by Edmund Brisco Ford in 1940 as: "the occurrence together in the same habitat of two or more discontinuous forms of a species in such proportions that the rarest of them cannot merely be maintained by recurrent mutation or immigration".
  • Transient polymorphisms occur when conditions in a habitat change so that one form is being replaced by another.
  • In contrast to transient polymorphism, many polymorphisms are actively maintained in a population by natural selection, and there are a number of ways in which this may occur:
    • Heterozygotes may be of superior fitness, but continually generate less fit homozygotes within the population
    • Presence of gradients of selective forces favoring one morph at one end of the gradient and another form at the other
    • There may be frequency-dependent selection in which each of the morphs of a species is fittest when it is rarest
    • Selective forces may operate in different directions within different patches in the population

Questions

  1. What is the difference between polymorphism and ecotypes?
  2. What is polymorphism?
  3. What are ecotypes?

Thursday, October 2, 2014

Geographic Variation within Species: Ecotypes

Digest

  • ecotypes: geographic variation within species
  • local adaptation can occur within the same species
  • there are experiments that can be done to check if two populations of a species at different environments have undergone local adaptation
  • examples of plants that have been locally adapted (populations at high and low altitudes) and plants that have not been locally adapted (dispersed at distances starting from 0.1 to 2000 km apart)
  • experiments are done by transplanting members of both populations under investigation at the same environment then measuring to see if differences between them appear
  • there can exist a balance between local adaptation and hybridization: "local selection by no means always overrides hybridization"
Ecotype experiment
Ecotype experiment

Questions

  • Which of the two are considered to be ecotypes?
  • Are the different ones still considered of the same species?

Questions

  1. How can experiments be made to test the interaction between hybridization and specialization (divergence)?
  2. What are ecotypes?

Wednesday, October 1, 2014

Specialization within Species

Thoughts

The idea of mobility makes me think about people of Upper Egypt and how their mingling with Egyptians from the Nile Delta area creates a sort of hybridization which is healthy. On the other hand, people who live in Siwa and have been more or less in isolation from the external world for thousands of years have been forced to adapt more to their environment. Also people who live in Aswan in Egypt and are Nubians might have less genetic variation and are more adapted to their environment.

Digest

  • The term species will be defined in the next section.
  •  An ecotype was coined in 1922 by Göte Turesson for plant populations "to describe genetically determined differences between populations within a species that reflect local matches between the organisms and their environments."
  • Only if the forces favoring divergence are strong enough to counteract the mixing and hybridization of individuals from different sites and  there is sufficient heritable variation on which selection can act evolution then forces the characteristics of populations to diverge from each other.
  • Immobile organisms become differentiated most notably while mobile organisms are less exposed to the forces of natural selection and therefore do not have to match themselves to a fixed environment as much as immobile organisms have to.

Questions

  1. Why is there no continuum of species along a spectrum of variation among organisms?
  2. What is the definition of a species?
  3. What about variation within the same species according to the environment they live in?