Unit B

Module 4 ~ Lesson 1


Read "The Need for Reproduction", "Mitosis", and "Meiosis" on pages 74 to 75 of your textbook. This material was covered in Science 10.

Read "Adaptations and Survival" and "Variation within a Species" on pages 114 to 118 of your textbook.


Variation is all around you — it's the differences between all living things. No two puppies or humans look and behave exactly the same. Some variations may give an organism a survival advantage, some may cause a disadvantage, and some will not make a difference in the organism's survival.

A variation that gives a survival advantage to an individual is called an adaptation. Adaptations allow an individual to survive and reproduce. When an organism reproduces, it can pass on adaptations to its offspring, giving them the same survival advantages. These adaptations continue to be passed on from parent to offspring over many generations as long as the adaptation gives the organism a survival advantage.

If the environment changes, an adaptation that once gave a survival advantage may now give a survival disadvantage to an organism. In the new environment, the organism will not survive to pass on its genetic information.

Variations can be created during sexual reproduction (when genetic material from both parents is mixed up) or through mutations.

Image by PIRO4D from Pixabay



Yes. Smell helps sharks survive by being able to find food in the vast ocean.
Kittens with the same parents can have many different looks based on the inherited combinations of genes that can occur during sexual reproduction.
A mutation in a somatic (body) cell cannot be passed on to the next generation. A mutation in a reproductive cell (egg or sperm) may be passed on to succeeding generations.
An example of a selective advantage is a mutation in houseflies. This mutation makes the insects resistant to the insecticide called DDT. This situation is only advantageous if DDT is being used because the flies with the mutation will have a better chance of survival and reproduction (survival of the fittest).
An example of a selective disadvantage can also be the mutation in houseflies that makes them resistant to DDT. This mutation reduces the growth rate of these flies. If DDT is not present, those flies will be less likely to survive and reproduce because of their smaller size (survival of the fittest).