Biological Evolution Standard B – 5.3

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.

Key Concepts Species Gene Pool

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.

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.

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

Vocabulary Genetic variation Allele frequency

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

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.

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

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

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

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

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