chapter 2 biology and evolution. chapter outline what is evolution? what are the forces...
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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.
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