Lamarck's Evolution

French botanist-geologist, said that evolution is an adaptive process whereby organisms acquire traits or characteristics during their lifetimes and pass these acquired traits on to their descendants. (Giraffes originally had short necks, stretching for leaves, made them grow longer necks).

Darwin and Wallace - Evolution

Natural Selection - organisms possess heritable variations (size, speed, agility, etc. Some of these variations are more favorable than others for survival (acquiring resources and avoiding predators). Not all young survive to reproductive maturity. Those with favorable variations are most likely to survive and pass on their favorable variations (descent with modification).

Natural Selection Examples

Finches on Galapagos Islands, Peppered moths, and Mantis.

Mendel's Experiments

He showed that genes controlling the same trait occur in alternate forms or alleles. One allele may be dominant over another. He coined the terms recessive and dominant. Each parent contributes one allele of each pair to the offspring.

Chromosomes

Chromosomes are complex threadlike chromosomes, double-stranded, helical molecules of DNA. The number of chromosomes is the same for a single species but varies among species. Fruit flies have 4 pairs, humans have 23 pairs, and horses have 32 pairs.

Meiosis

a type of cell division in which sex cells form. Each cell contains one member of each chromosome pair. Only one of the four final cells is functional. 1 cell with 4 -> split cell with 2 x's on each side -> two cells with 2 x's -> four cells with 2 strands each.

Mitosis

the complete duplication of a cell. A cell has four chromosomes (2 pairs) produces two cells, each with four chromosomes. Mitosis occurs in all body cells except for sex cells. Once an egg is fertilized, the developing embryo grows by mitosis. 1 cell with 4 -> 1 cell with line of 4 x's -> two cells with 4 strands each.

Speciation

The origin of new species. Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.

Reproductive Isolation Types and Explanations

1. Mutation - can cause instant reproductive isolasion and speciation because the mutant individuals are genetically blocked from mating with members of the non-mutant population. 2. Geographic barriers - prevent new traits that evolve in one population from being introduced to other populations. Geographically separated populations may develop genetic traits that preclude interbreeding.

Allopatric Speciation

the formation of new species by geographic isolation. when a small part if a population becomes isolated from its parent population and gives rise to a reproductively isolated species due to environmental factors.

Rate of Evolution

evolution and speciation via natural selection occured mainly as a slow and gradual process

Punctuated equilibrium

The fossil record shows that new species appear suddenly, then persist unchanged for millions of years, and then disappear just as suddenly.

Three types of evolution

Divergent evolution, Convergent evolution, and Parallel evolution.

Divergent Evolution

ancestral species giving rise to diverse descendants adapted to various aspects of the environment (Galapagos finches - adaptive radiation)

Convergent Evolution

the development of similar characteristics in distantly related organisms, due to adapting to similar environments (Marsupial carnivore and saber-toothed tigers)

Parallel Evolution

similar characteristics arising in closely related organisms but not from a common ancestor, due to adapting to similar environments (kangaroo rats and jerboas)

Biological evidence for evolution

Homologous organs, Analogous organs, and Vestigial structures

Homologous organs

similar arrangement of bone, muscle, and tissue in different organisms modified for different functions (forelimbs of humans, whales, dogs, and birds)

Analogous organs

serve the same function in different organisms, wings of insects and birds, quite different in structure and developments.

Vestigial structures

nonfunctional or partly functional remnants of structures that were functional in their ancestors (dogs have tiny nonfunctional toes on their back feet)