Natural Selection and Variations

Natural Selection & Evolution

LO - Understand Darwin's theory of evolution by natural selection

Open Ended

What are the two causes of variation in organisms?

Open Ended

Why is there genetic variation between organisms of some species?

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What do we mean when we say that two organisms belong to the 'same species'?

Open Ended

What might organisms of the same species compete for?

Poll

Evolution is when an organism changes its characteristics so that it can survive in its environment.

• True

• False

Evolution is something that happens to entire species

NOT

to individual organisms

In this picture, the species of mice has evolved to become predominantly black.

Example -

Evolution of beetles

1. At first, the population of beetles has somewhat equal numbers of brown and green beetles. This is genetic variation.

2. Green beetles are easier to spot than brown beetles, so the birds eat more green beetles.

3. This means more brown beetles can survive and reproduce.

4. Over time, the population of beetles contains mostly brown beetles!

Open Ended

Why did the species of beetles evolve to become mostly brown?

Open Ended

Suggest a reason why this species of worm has evolved to become entirely green over time.

Selective breeding VS Natural selection

Let us compare these two processes

Selective Breeding

When humans choose animals (or plants) with desired characteristics to breed.

This is so that we end up with large populations of the organism with the desired characteristics.

Humans can use them.

Multiple Select

Which 2 chickens would a farmer select to breed together if he sells eggs?

• A

• B

• C

• D

Open Ended

EXPLAIN which chickens a farmer would select to breed together if he sells eggs?

Open Ended

EXPLAIN which chickens a farmer would select to breed together if he sells chicken meat.

Open Ended

What is the difference between natural selection and selective breeding?

Check your understanding of natural selection

A few questions to check

Open Ended

Which organisms are most likely to survive, reproduce, and pass on their genes?

The ones which are...

Open Ended

ALL desert plants have very long roots that can reach underground water.

Suggest why all desert plants are this way.

(Why aren't there any plants with short roots?)

Useful links

• https://blogs.ubc.ca/mrpletsch/2019/10/18/unit-2-3-mechanisms-of-evolution-and-natural-selection/

• https://evolution.berkeley.edu/evolibrary/search/imagedetail.php?id=281&topic_id%3D%26keywords%3D