Chapter 2

Biology and Evolution

Chapter Outline

What is Evolution? What are the forces responsible for

Evolution? What is the molecular basis for

Evolution?

Linnaeus Classification System

Body structure Body function Sequence of bodily growth

Classification of Humans

Kingdom Animalia

Phylum Chordata

Subphylum Vertebrata

Class Mammalia

Order Primates

Classification of Humans

Superfamily Hominoidea

Family Hominidae

Subfamily Homininae

Genus Homo

Species sapiens

Natural Selection

Based on two observations: All organisms display a range of

variation. All organisms have the ability to expand

beyond their means of subsistence.

Evolution

Occurs as genetic variants in the gene pool of a population change in frequency.

Genes, the units of heredity, are segments of molecules of DNA (deoxyribonucleic acid).

DNA

Human DNA

Provides the instructions for the thousands of proteins that keep us alive and healthy.

Molecules are able to produce exact copies of themselves.

DNA molecules are located on chromosomes, structures found in the nucleus of each cell.

Chromosomes

Each organism has a characteristic number of chromosomes, usually found in pairs.

Humans have 23 pairs. Genes located on paired chromosomes

and coded for different versions of the same trait are called alleles.

Structure of a Generalized Eukaryotic Cell

Cell Division

Mendel’s Law of Dominance and Recessiveness

Dominant alleles are able to mask the presence of recessive alleles.

The allele for type A blood in humans, is dominant to the allele for type O blood.

Alleles that are both expressed when present are co-dominant.

An individual with the alleles for type A and type B blood has the AB blood type.

Evolutionary Forces

Mutation - happens when copying mistakes are made during cell division.

Genetic drift - the effect of chance events on the gene pool of small populations.

Gene flow - the introduction of new alleles from nearby populations.

Evolutionary Forces

Interspecies gene transfer - the transfer of genes between unrelated organisms.

Natural selection - the environment exerts pressure that selects individuals to reproduce the next generation.