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