Chapter 7 Review Also refer to Essential Questions for Chapter 7
Terms: allele, allopatric speciation, chromosome, convergent evolution, divergent evolution,
parallel evolution, DNA, gene, inheritance of acquired characteristics, mutation, natural
selection, adaptation, phyletic gradualism, species, homologous structures, analogous
structures, theory of evolution, Darwin, Lamarck, Mendel
Evolution: process whereby organisms have changed since life originated
**organisms have descended with modification from ancestors that lived during the
past**
Darwin spent 5 years on a voyage where he observed and collected various species.
His observations led him to propose the mechanism for evolution – natural selection.
Darwin’s observation of finches and mockingbirds isolated on ocean islands in the
Galapagos caused him to believe they had a common ancestor but were naturally
selected by the food sources on the islands.
Darwin’s observation of “artificial selection” used by animal and plant breeders helped
him formulate his ideas.
Darwin published “On the Origin of Species” 20 years after his voyage.
Darwin shared the discovery of the natural selection with Alfred Wallace; however
Darwin receives the credit.
Natural selection: *Organisms in all populations possess heritable variations.
*Some variations are more favorable than others.
*Those with favorable variations are more likely to survive and reproduce to pass on
their favorable variations.
Natural selection works on existing variations within populations.
George Mendel: 1860s (he was an Austrian monk)
Controlled experiments with garden peas that always produce offspring with same
traits.
Recognized that variations on genes (called alleles) were responsible for the color of
the flowers.
Dominant variations (red flower) would be expressed any time the R (red) allele is
present. If the r or white flower allele is expressed, white will only occur if both white
alleles are present in offspring.
Conclusion: The factors that control characteristics are controlled by alleles on genes.
Traits do not blend. The genetic variations are carried to future generations even if not
expressed in the parents.
DNA:
`molecules form chromosomes is found in cells of all organisms (note: the
chromosomal material in bacteria differ from other organisms)
Chromosome theory: changes in genes (mutations) are one source of variation in populations.
(Note: the variations are expressed in populations, not just in individuals)
Mutations: chromosomal mutations affect large areas of the chromosomes; point mutations
affect a particular gene.
only inherited if mutations affect sex cells
mutations can be harmful, beneficial or neutral.
causes include radiation exposure such as x-rays, ultraviolet radiation, and chemical
exposure. some occur spontaneously.
species: organisms within a population that reproduce fertile offspring
allopatric speciation: species arise when a small part of a population becomes isolated.
phyletic gradualism: accumulation of minor changes in a population eventually lead to new
species over a long period of time.
punctuated equilibrium: little or no change takes place in a species; then evolution occurs
rapidly giving rise to new species in a short time.
divergent evolution: species that descend from a common ancestor differ significantly over time
convergent evolution: organisms that are distantly related develop similar characteristics
independently (result of adaptation to similar environments)
parallel evolution: similar characteristics develop among closely related organisms in
comparable environments
background extinction: continual extinction of species over time.
mass extinction: accelerated extinction rate charply reduces diversity of life forms.
Evidence for evolution:
physical: embryology, comparative anatomy, geographic distribution, fossil record
similarities among life forms (body types, limbs, skeletal)
scientific: ability to predict , including the current and past findings.
See Table 7.1
chromosomal: DNA shows biochemical similarities and genetic connectivity
homologous structures: similarly structured anatomy that is modified in different organisms for
different functions (forelimbs of whales, dogs, birds)
analogous structures: dissimilar structured anatomy that serves similar functions in different
organisms (wings of insects and birds)
fossil succession: fossil record shows a sequence of organisms worldwide. single-celled, multicelled, invertebrate animals, vertebrate animals; succession of fish, amphibians,
reptiles, mammals, birds
(see Fig. 7.20)
Missing links: yes, there are missing links in the fossil record.
there are intermediate organisms in the fossil record that contain traits of earlier groups
and later groups.
link found between fish and amphibians
manatees (sea cows) aquatic mammals with limbs (ancestors were land animals)
other??