1. Biological Evolution
Standard B – 5.3

2. Standard B-5
The student will demonstrate an understanding of biological evolution and the diversity of life.
Indicator B – 5.3: Explain how diversity within a species increases the chances of its survival.

3. Key Concepts
Species
Gene Pool

4. What You Already Know!
In the 6th grade, you recognized the hierarchal structure of classification. In the 8th grade, you explained how biological adaptations of populations enhance their survival in a particular environment.

5. What You Should Understand After This Lesson
What a species is
Species share a gene pool
Within a population, there is variation
How is variation beneficial to the survival of the species?
Natural selection acts on phenotypes that are determined by genotypes.

6. Objective
Summarize the ways that diversity affects a species chances of survival.
Explemplify favorable traits that ensure reproductive success or species survival.

7. Vocabulary
Genetic variation
Allele frequency

8. Genetic Variation
A population shares a common gene pool. There is great genetic variation among the individuals within a population.

9. Genetic Variation
Sharing genetic variation leads to phenotypic variation.
This is necessary for natural selection.
Genetic variation is stored in a population’s gene pool.
Genetic variation is measured by allele frequency.
Measures how common an allele is in a population.
Can be calculated for each allele in a gene pool.

11. Pea Plant Example
There are 5000 pea plants in this field. Within this population, there are both tall and short plants.

12. What Causes Genetic Variation?
There are many ways for genetic variation within a population to occur.
Mutations
Recombination
Hybridization

13. Mutations A change in the DNA Can form new allele combinations
Can be passed on only if in the gametes (sex cells).

14. Recombination Forms new allele combinations Occurs during meiosis
Crossing over
Parent’s alleles are rearranged in offspring
Can be accomplished through genetic engineering.

15. Hybridization Crossing of 2 different species
Occurs when individuals cannot find a mate
Topic of scientific research