Evolution

Comparing Anatomical Evidence

Fossil Evidence

Embroyological Evidence

Homologous vs Analogous

Transitional form

discovered 2 years after Darwin publish "On the Orgin of Species"

relative dating

comparing fossil 's ages by where they are found in the the earth

organisms that show the inter mediate states between an ancesteral form and that of its descendants

Radioactive dating

radioactive elemnets in fossils or sedimentas surrounding fossils

Homolgous Structures

Whales and Hummingbirds both inherited their skeletons from a tetrapod ancestor

similar structures in related organisms that are a result of common ansestery

Their bodies have been modified and parts have been lost through natural selection, resulting in adaptation to their repestive life styles over millions of years

Vestigial Structures

Homologous

Analogous

characteristics in different organisms that are similar because they were in herited from a common anscestor that also had that characteristic

Common ancestery/desent

when one speciesisthe ancesto of two or more species later in time

Ex: Forelimbs of tetrapods

have seperate evolutionary orgins but are similar because they have both experienced natural selection that shaped them in a similar wy

Convergent evolution

process in which two distinct lineages evolves a similar characteristic independently of one another

Ex: Flight in bats vs flight in birds

Homologous structures observed during early embroyacial development

These homologous structures may not be visivle in the fully developed organism

Molecular Evidence

Amino Acid sequences

chromosomes

DNA sequences

...can all become paired to determine relatedness of organisms

gene expression

which genes are turned on/off

timing

For example, we can learn about the evoulution of humans and our closest living relative, the chimpanzee, by comparing chromosomes

humans have 23 pairs of chromosomes, while chimpanzees have 24 pairs

little or no purpose to present organism, but provide evidence for common ancestry

Mutation

a change in a DNA sequence

occurs because of replication or repair

random

the ultimate source of genetic variation

can be beneficial, neutral or harmful

the only mutation that matter are genetic offspring mutations

Migration/Gene Flow

movement of individuals, and their genetic material, from one population to another

Ex: pollen being blown to a new destination

If gene versians are carried to a population where these gene previously didn't exist, gene flow can be a very important source of genetic variation.

Natural Selection History

Genetic Drift

genetic drift affects genetic makeup of the population, but unlike natural selection, through an entirely random process

doesn't work to produce adaptations

In each generation, some individuals leave behind a few more desendants than other individuals -- by chance

Charles Darwin and Alfred Russel Wallace

Thomas Malthus published a bookin 1797 called "Essay on the Principle of Population"

struggle for existance

Darwin and Wallace both realized that if an animal has some trait that helps it to withstand the elements or to breed more successfully, it may leave more offspring behind than others. On average, the trait will become more common in the following generations.

On the Orgin of Species

one of the most influential scientific books of all time

Charles Darwin

A visit to Galapagos Islands in 1835 helped Drwin formulate his ideas on natural selection. He found several species of finches adapted to different enviromental hiches. THe finches also differed in beak shape, food source and how food was captured

Natural Selection

Variation of traits

Heredity

Carrying capacity

differential reproduction=not all individuals get to reproduce to their full potential

when the above 3 criteria are met, evolution by natural selection will occur

Adaptation

a feather that is common in a population because it providessome improvised function

well fitted to their function and are produced by natural selection

Mimicry of leaves by insects is an adaptation for evading predaters

Adaptive Radiation

a single species evaluates into a number of other species

These species are distinct from one another, but are closly related

Each species is specialized

Sexual Selection

acts on an organisms ability to successfully copulate with a male

sexual selection makes many organisms go to extreme length for sex

sexual selection is often powerful enough to produce featuresthat are mmore harmful to the individual's survival

Ex: peacock feathers

Arificial Selection

instead of nature, people select which organisms get to reproduce

farmers and breeders allow only the plants and animals with desirable characteristics to reproduce

Ex: produce, pets, livestock

Co-evoulution

cases where to or more species reciprocally affect each others evolution

likely to happen when different species have close ecological interactions with one another

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Speciation

Species

a popuation of similar organisms that can interbreed to produce viable, fertile offspring

Speciation is a lineage-splitting event that produces two or more seperate species

Branching points on phylogentric trees are speciation events

Geographic isolation i an important step of some speciation events

Microevolution

small scale, single popuation

Macroevolution

large scale, across species