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is the theory that explains how change in a species occurs over time.

evidence such as fossil records indicate that...

life began on Earth more than 3 billion years ago

the first living organisms were...

single celled organisms, which over time become more complex

about a billion years ago...

more complex multicellular organisms began to appear

common ancestors

modern organisms evolved over long periods of time from these...

theory of evolution

-central theme of modern biology
-evolution helps us understand how the variations between individuals can lead to changes in an entire species

Charles Darwin

introduced the idea of evolution in the 1850's, which has since become an accepted theory


is a concept that has been tested and confirmed in many different ways and can be used by scientists to make predictions about the natural world

fossil record

- the theory of evolution helps us understand the similarities among organisms such as bone structure and biochemical make up
-history of life is revealed by this, which shows the history of Earth's organisms
-it also spans much of geologic time, the billions of years of Earths history

phylogenetic trees

evolution doesn't always show progress in a set direction for any species, but rather changes cause species to appear to grow like branches on a tree:
-some branches extend from beginning to present with little change
-some die off
-and some branch further
each branch represents a different species.
branching points show common ancestors of the species at the ends of branches

artificial selection of plants and animals by breeders

Darwin proposed that evolution was similar to this process...

natural selection

describes how organisms with desirable traits (random) survive in nature and are able to breed and pass on their genetic information (survival of the fittest)

evolutionary change depends on...

- overproduction
-supply of resources
-genetic variation
-selection by the environment


potential for a precise to increase its numbers

supply of resources

needed for life

genetic variation

due to mutation and genetic shuffling


-each species has the potential to produce more offspring that can possibly survive
-stable environments maintain populations at a constant rate from year to year based on resources

factors affecting survival:

-environmental conditions
-available resources
-ability to competition

genetic variation

-new traits that can lead to evolution come from this, its within a species, which is the unique combination of traits each organism inherits from its parents
-some variations are advantages when competing for resources

adaptive value

a trait that helps an organism survive and reproduce under a given set of environmental conditions has this...
ex.) coloration of a rabbit

a chnge in DNA causes a change in...

that organism

in sexually reproducing organisms only the changes in...

the sex cells or gametes are passed onto the offspring

two ways organisms can develop different genes that are different from its parents are...

-genetic shuffling


-change a base sequence of a DNA molecule
-are random events that cannot be predicted
-most are harmful and may cause death, however few are benefit an individual, increasing the chance of survival, reproduction, and passing this on to the next generation
-beneficial ones lead to the evolution of a new species

genetic shuffling

- the sorting and random recombination of genes during meiosis and fertilization resulting in new and different combinations of genes
- these genes are passed onto offspring

competitive advantage

traits with adaptive value in a specific environment gives individuals in that environment this...

a driving force to evolutionary change is...

a changing environment



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