Lecture 3: Biological Evolution - Genetics and Evolution

what are homologous chromosomes?

pairs of chromosomes that carry similar information and therefore are the same shape and size

what are genes?

information encoded into portions of chromosomes

how many pairs of chromosomes do humans have?

23

genes can encode for traits like…

eye color, height, personality

what is an allele?

alternate forms of a trait

how many alleles does each gene have?

2, one from each parent

what does homozygous mean?

having the same allele, either recessive or dominant (either AA or aa)

what does heterozygous mean?

having 2 different alleles, one recessive and one dominant (so Aa)

what does higher levels of heterozygosity in a population do?

increases genetic diversity and can increase ability of the population to survive in a changing environment

studies have shown that heterozygosity can be beneficial to some individuals for what reasons?

it may promote growth, metabolic efficiency, and health, all leading to greater chances of survival

how is heterozygosity related to population size?

as population size increases, so does heterozygosity

what is the genotype?

the alleles that an individual possesses (CC, cc, or Cc)

what is the phenotype?

the physical outcome of the alleles (crest or no crest)

what is the gene pool?

the sum of all the alleles in a population

variation occurs in the ______ that are carried by individuals of the population, but the outcome of the genes, the phenotype, is what ______ can act upon

alleles, evolution

what is evolution?

a change in genetics in a population over generations

why is sexual reproduction important?

it increases genetic diversity and the long-term survival of a species

what are 5 examples given as evidence of evolution?

fossil record, biogeography, comparative anatomy/embryology, molecular biology, lab and field experiments

what are 2 things that help increase chances of fossilization?

being buried in sediment (more likely in aquatic conditions) and if the animal has hard parts, like shells or bones

what are trace fossils? give examples

indirect evidence of biological activity by life in the past, such as tracks, burrows, nests, and dung

why are fossils important to our understanding of evolution?

• they suggest that the earth is very old

• they allow us to study evolution and evolutionary relationships by comparing animals

• they allow us to identify “living fossils”

• they may aid in conservation of species by knowing where they used to live, which can aid in reintroduction efforts

what is the burgess shale? how old is it? what is important about it?

a fossil shell in the Canadian rockies, 505 million years old. important because many of the fossils did not appear to fit into modern groups and soft bodied organisms were fossilized more than normal

what are living fossils?

animals alive today that have not changed much over millions of years, such as the nautilus, the horseshoe crab, and the coelocanth fish