Chapters 21,

Front 1

Natural selection

Back 1

An evolutionary mechanism that occurs when some individuals of a population are better able to adapt to their environment and, subsequently, produce more offspring.

This mechanism of evolutionary change was first described by Charles Darwin. He observed the changes in the shapes of the beaks of finches in response to the available food supply.

4 conditions of natural selection:

1. Individuals within species are variable

2. Some of these variations are passed on to offspring

3. In every generation, more offspring are produced than can survive

4. The survival and reproduction of individuals are not random: Individuals who survive and go on to reproduce are those with the most favorable variation

Front 2

biological evolution

Back 2

It is a series of heritable changes resulting from progressive accumulation of alterations of DNA sequences in a population of organisms that occurs over time. The term is also frequently used to refer to the appearance of a new species.

Front 3

What does natural selection lead to?

Back 3

Adaptation

Front 4

Molecular

Back 4

molecular changes in genetic material that lead to phenotypic changes. Microevolution relates to changes in a single gene or allele frequency (small scale) in a population over time.

Front 5

evolution evidence

Back 5

- embryonic development
- vestigial structures
- distribution patterns
-convergence
- molecular

Consider: The theory of evolution has many lines of supporting evidence.

Front 6

species

Back 6

group of related organisms that share a distinctive form

Front 7

endemic species

Back 7

is one that is naturally found only in a particular location

Front 8

radioactive isotope decay (absolute dating)

Back 8

A technique used in dating a rock to predict the age of the fossils (preserved remains of one-living organisms) occurring in the rocks. The known half-life is the amount of time it takes for half of the isotope to change into another version of the element, so the older the rock the more radioactive decay or change. This technique allows scientists to date the fossil record reasonably well.

Front 9

fossil evidence of evolution

Back 9

progressive changes in fossils of different ages strongly document evolutionary transitions; Archaeopteryx is oldest known bird fossil. It possesses some ancestral traits and some traits of present day birds (feathers); In the case of the toothed whales, the fossil record shows they evolved from a land mammal with hooves; in the case of the horse, natural selection favored traits that allowed the animals to survive in emerging grasslands

Front 10

convergent evolution

Back 10

independent evolution of similar forms in different lineages when exposed to the same selective pressures, i.e., Australian marsupials and placental mammals of other continents or the fish form in response to the physical properties of water

Front 11

biogeography

Back 11

studies of geographic distribution of species

Front 12

homologous anatomical structures/molecular functions

Back 12

seen in related species; are derived from the same body part in a common ancestor and share a common developmental pattern but may have different appearances and functions

Front 13

analogous structures

Back 13

structures that are similar in form due to function determining the necessary form, not because of a common ancestor

Front 14

divergence

Back 14

evolution of different forms in the same lineage when exposed to different selective pressures

Front 15

artificial selection

Back 15

Human manipulation of organisms' environment or breeding success results, as in the case of dogs, in many phenotypes and in some cases maladaptive structures that would not allow the organisms to survive in the natural world; in the case of bacteria, it has resulted in antibiotic resistant strains.

Front 16

domesticated species

Back 16

exhibit more phenotypic variation than non-domesticated because of artificially controlled environments in which they exist; many would not survive in the natural world

Front 17

anatomical evidence for evolution

Back 17

strongest evidence supporting evolution comes for developmental comparisons reflecting descent from a common ancestor; early vertebrate embryos possess pharyngeal pouches that develop into glands and ducts in humans and gill slits in fish; mammals have 7 vertebrae

Front 18

vestigial structures

Back 18

have no obvious function, but resemble structures their ancestors possessed, e.g., side toes of a horse, the pelvis of the whale, and the human appendix (homologous)

Front 19

homology

Back 19

fundamental similarity due to descent from a common ancestor

Front 20

Molecular homologies

Back 20

all organisms use DNA to store information, the access to cellular information is via RNA, proteins are the functional products of most genes, and there are similarities in biochemical pathways in all life.

Front 21

molecular evolution

Back 21

molecular changes in genetic material that lead to phenotypic changes; tested by comparing sequences of amino acids of various proteins in different species

Front 22

Orthologs

Back 22

are homologs produced by speciation. They represent genes derived from a common ancestor that diverged due to divergence of the organisms they are associated with. They tend to have similar function.

Front 23

Paralogs

Back 23

are homologs produced by gene duplication. They represent genes derived from a common ancestral gene that duplicated within an organism and then subsequently diverged by accumulated mutation. They tend to have slightly different functions

Front 24

exon shuffling

Back 24

different exons either within a gene or between two nonallelic genes are occasionally mixed which can quickly create novel multidomain proteins, leading to increased variance in species

Front 25

horizontal gene transfer

Back 25

movement of genetic material between different species; other than by descent in which information travels through the generations as the cell divides