Must Know High School Biology by Kellie Ploeger Cox

Author:Kellie Ploeger Cox
Language: eng
Format: epub
Publisher: McGraw-Hill Education
Published: 2019-03-17T16:00:00+00:00

2. There are usually too many offspring for the environment to support, because resources are limited.

The idea of overproduction rolled around in Darwin’s mind after he read Malthus’ essay on human population growth. This is a really important thing to consider for the process of natural selection, because if the environment would support unlimited numbers of offspring, natural selection wouldn’t occur. As it is, however, exponential growth is only possible with unlimited resources, no predators, and no disease … and that’s not likely.

3. There’s a lot of competition, and any individual who happened to have been born with a helpful trait is able to outcompete others in the population.

Environments place limits on population growth because, as we mentioned above, an environment just can’t provide unlimited space and resources. So, this leads to an epic struggle for food, water, and shelter … and some organisms are more successful than others.

4. This most-fit individual gets to survive and reproduce. By doing so, the survivor’s “most-fit” genes are now passed onto the next generation, resulting in an adaptation.

Certain variations allow an individual to outcompete others and win that struggle for resources. An adaptation is a helpful trait found in a population that is the product of natural selection. Natural selection accumulates these adaptations because they help an individual survive and reproduce.

As so often happens in science, this simple concept has hidden pitfalls in the form of misconceptions. I will cover three important points that are easy to misunderstand.

■ You gotta be born with it.

It’s super, super important to understand that any trait that helps an individual survive must be genetic and heritable, otherwise it doesn’t count (sorry, Lamarck). Only those qualities that can be passed onto the next generation (in their genes) have an impact on the next generation’s genetic makeup (gene pool). If, for example, an octopus developed super-stretchy legs during its lifetime and allowed it to better reach a crab hiding in the rocks, that doesn’t result in evolution. Sure, that one octopus will be better able to find food and survive, but it cannot pass on its improved stretchiness to its offspring unless it was a genetic trait it was born with.

The reason I keep stressing that “you gotta be born with it” is because even though we accumulate genetic mutations during our lifetime, that doesn’t mean your kids will inherit any of those mutations. What if, for example, you got radioactive waste on your hands and it caused genetic mutations in your fingertips so they grew suckers that allowed you to climb walls. Super cool, right? But would this mutation be passed on to the next generation? To answer that question, think about this, where are the genes to make the next generation coming from? Yup, the egg and sperm.

In order for you to pass on some helpful mutation, you need to be born with it because it needs to be in your gametes (egg or sperm). And in order for a certain gene to be found in the

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