LO 7 : Evolution (Part 1) | BiologyofEverything

The process of natural selection can be understood in terms of gene pools. A gene pool is the total collection of genes in a population at a given time. The traits that are present in a population at a given time are determined by the gene pool. If a trait is advantageous and increases an individual's chances of survival and reproduction, it becomes more prevalent in the gene pool over time.

1. Evolution and Natural Selection

What is Evolution?

Evolution is the process by which modern organisms have descended from ancient ancestors. This process, known as descent with modification, occurs over many generations through a combination of natural selection and genetic change.

How does it work?

Natural selection, also known as "survival of the fittest," is a basic mechanism of evolution. It occurs when individuals with characteristics that increase their chances of survival are more successful and pass these characteristics from one generation to the next. Over time, these characteristics become predominant within a population.

Mutations, which are changes in an organism's genetic material, also play a role in natural selection. If a mutation gives an individual an advantage in its environment, it is more likely to survive and reproduce. Over time, these advantageous mutations can become a predominant characteristic within a population.

2. Evidence of Evolution

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What is Extinction?

Extinction is the dying out of a species because it cannot adapt to new environmental conditions. This can occur naturally as part of the evolutionary process, but it can also be caused by human activity such as habitat destruction, overhunting, and pollution.

Mass extinctions, which are periods of time in which a large number of species go extinct in a relatively short period, have played a significant role in evolution. These events can have a drastic effect on the diversity of life on Earth and can free up niches for new species to evolve and fill.

What is the evidence of evolution?

Structural and embryonic similarities between different organisms. Eg: similar bone structures in the forelimbs of animals such as birds, bats, and whales suggests that they may have evolved from a common ancestor.
Geographic distribution of organisms. Eg: species in certain geographic regions only such as the kangaroo

3. Fossils are used as evidence of evolutionary trends because they provide a record of ancient life. By studying the characteristics of fossilized organisms, scientists can learn about the evolutionary relationships between different species.Below is a simple example using fossil evidence to show the evolutionary trend of whales over 50 million years. It shows changes such as
(a) Removal of hind legs
(b) Change in the shape of the skull to make sonar possible

3. Example of Evolution

During the Industrial Revolution in England, the trees where the peppered moth lived became covered in soot from factories.
This made the lighter-colored moths more visible to predators, while the darker moths were better camouflaged.
The lighter moths had a disadvantage and were less likely to survive and reproduce.
A mutation for darker coloration occurred in some individuals, giving them a survival advantage.
The proportion of darker moths in the population increased over time due to natural selection.
The trait for darker coloration became more prevalent in the gene pool as a result.

Why do some species evolve faster than others?

While some species have changed significantly over time, others have remained almost unchanged. These species, known as "living fossils," have low diversity and have persisted for long periods of time. An example of a living fossil is the coelacanth, a type of fish that was thought to have gone extinct 66 million years ago.

Why has the coelacanth been so successful?

One possibility is that it has been successful in adapting to its environment and has had few predators, allowing it to survive and reproduce without the need for significant evolutionary changes.
Another possibility is that the coelacanth has a simple life cycle and reproductive strategy, which allows it to survive and reproduce in a wide range of conditions. It may not have been exposed to the same selective pressures that have led to the evolution of other species.