|Evolution and Coevolution
The Tree of Life keeps branching and leafing, and through time, species change to more effectively "fit" with their place to live and their way of making a living (getting energy). Their place and way together are called an ecological niche.
Natural adaptation is a branching process so slow that we don't ordinarily see it happening, but we do see it in microorganisms, which have millions of generations to one human generation (about twenty years).
Over vast stretches of time measuring hundreds of millions of years, species of life change in many ways. The forms of species change over long periods of time in the process called evolution.
When a population of a species is sufficiently separated from others, by location or by niche (including feeding habits), their adapations become different enough that they become a new species. The diversity of bodily forms on Earth is amazing and filled with wonder.
Where does this giraffe make a living?
Co-evolution is the process in which species slowly transform together toward a mutual "fit". Evolution is mutual, and it takes place in communities, even though we often think of it only at ther species level.
Our new knowledge of ecology is teaching us to become aware that nature is usually cooperative, rather than competitive.
The key to adaptation is variation. Variation is difference. Within each species, there are thousands of small differences. The young of almost all species have small differences among them.
In humans, we cherish those differences because they make us individuals. Almost every living organism is an individual, not exactly like any other member of its kind. (The exceptions are the offspring of females who lay unfertilized eggs in some roundworm and insect species, and in a few lizards. These offspring are virtual copies of Mom. Other exceptions happen when organisms reproduce asexually--create a new individual by budding, like polyps, for example.)
These many little differences within a species make it possible for some offspring of that species to change in response to changing conditions in its environment.
As species, our differences are our strength. For all species, diversity is strength.
Variation is "hard-wired" into all living things.
The key to survival is difference. Without the continual flowering of difference (or variation) a species will not last. It will die out (go extinct).
Biological variation, or difference, is what keeps a species going.
bill variation in galapagos finches
About 100,00 years ago, a pair of South American finches flew to the Galapagos Islands. Once there, where there were no other finches and no predators, the pair reproduced and gradually, over many generations, filled thirteen different ecological niches and became thirteen species. This process of species-formation is called adaptive radiation. For instance, one finch population evolved a longer bill and the ability to use sticks to prod insect holes in cactus, and over time evolved into the woodpecker finch. Other finches evolved thicker bills for eating the large seeds of the prickly pear cactus, and became the large ground finch; smaller thick bills were ideal for eating small seeds; while other bills and habits adapted themselves to insect predation. They share the same general space, but exploit different feeding opportunities within it. The effect is cooperation. Charles Darwin visited the Galapagos Islands in the 1830s and studied the finches he found there. This experience helped him grasp the process he named evolution. You could say that the theory of evolution flowed from the beaks of small birds.
How does all this variation or difference happen? The answer is mutation.
Organisms grow and reproduce by copying their genetic material, creating eggs and sperm. Mutation is a continual process of tiny changes that happen as cells copy themselves. When genetic material is copied within the cell, little changes happen, so the copy is sometimes not quite perfect. Amazingly, that can turn out to be a good thing. Little copying errors in the reproductive cells add up to create variation within the species, so what look like mistakes turn out to be the differences that allow a species to adapt. On the other hand, many mutations are lethal.
Mutation is a natural and inevitable process. Mutations can be triggered within the cells in unnatural ways, however. Many human-made chemicals cause mutation, as can radiation. Mutation as a result of human activity is usually a bad thing, which leads to deformities and death.
In contrast, mutation that occurs naturally is generally a good thing for a species, even though most mutations result in death for individual offspring. Natural mutations make it possible for a species to change and survive and flourish in response to changes in its living conditions. This process of change to better fit new circumstances is called adaptation.
The more exactly or tightly an organism adapts to its niche, the more specialized it becomes. If an animal is perfectly adapted to its niche for a long time it may lose the ability to change if the niche changes.
This Mountain Gorilla is over-specialized and will probably soon go
extinct as its habitat disappears under human pressure.
Drawing © Owen Caddy
As natural communities of plants and animal co-evolved, some animals became specialists without becoming too specialized.
Hummingbird beaks fit tubular flowers
Painting © Owen Caddy
Hummingbirds beaks and tongues adapted to fit inside long tubular flower structures. Or, Long tubular flowers adapted to fit hummingbird beaks. Both statements are true. That's how co-evolution works--the whole process is continuous and reciprocal. The tubular flowers also adapted to produce sugar nectar at their bases. That sweet food is what drove this adaptation. Small insects adapted to live in the flower tubes as well--free protein! Humminbird tongues adapted to carry barbs which pluck the insects right out of the flower.
The feet of animals that climb for a living often adapt.
Which frog foot is adapted to climb?
Some adaptations seem odd until we understand their function. Why would a fish have wings?
drawing © Owen Caddy
Flying fish can sail above the waves for many yards. They "fly" to avoid being eaten. When a school of flying fish is attacked by predator fish or dolphins, the whole school swims rapidly and propel themselves out of the water with strong tails.
Adaptations are slow changes in response to pressures from outside the organism. Adaptations change both bodies (forms) and behaviors.
Life keeps adapting to changes in its environment, and it keeps trying to fill up all possible environments. When mountains form, plants adapt to new heights and colonize it; then the animals adapt and move up.
This llama is a cousin of camels that adapted to high altitude in the Andes Mountains altiplano of Bolivia and Peru.
Llamas' adaptations include huge lungs, thus more efficient oxygen transfer. Their blood also carries more red blood cells than the blood of animals adapted to lower elevations. It is cold at high altitude; their heavy wool is famous for warmth.
What adaptations do you think humans might have to high altitude?
People who live high in the Andes on the altiplano have "barrel chests" to hold large lungs, and short legs, to reduce heat loss from surface area. They also have very thick skin on the soles of their feet, with many more blood vessels than lowland people, so their feet don't freeze.
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