Natural Selection Flashcards
Charles Darwin traveled around the world on the
HMS Beagle
Charles Darwin observed organisms on different islands that were clearly similar, yet distinct differences which lead to the idea of
natural selection
3 principles of natural selection
1- most characteristics of organisms are inherited, or passed from parent to offspring
2- more offspring are produced than can survive, so resources for survival and reproduction are limited
3-offspring vary among each other in regard to their characteristics and those variations are inherited
Alfred Wallace
naturalist who made similar observations as Darwin
papers by darwin and wallace presenting the idea of natural selection were read together in 1858 before the
linnenan society by londaon
Natural selection can only take place if there is
variation, or differences, among individuals in a population
The differences that allow natural selection to occur must be
some genetic basis
genetic diversity in a population comes from two main mechanisms:
mutation and sexual reproduction
mutation, a change in DNA is the
ultimate source of new alleles, or new genetic variation
sexual reproduction-
2 parents reproduce, unique combination of alleles assemble to produce the unique genotypes and thus phenotypes in each of the offspring
how do we acchieve genetic diversity?
mutations and sexual reproduction
A heritable trait that helps the survival and reproduction of an organism in its present environment is called an
adaptation
Whether or not a trait is favorable depends on
the environment conditions at the time
The same traits are not always
adaptive because the enviroment can change
Sometimes, evolution gives rise to groups of organisms that become
tremendously different from each other
When 2 species evolve in diverse directions from a common point, it is called a
divergent
convergent evolution occurs when
similar traits evolve independently in species that do not share a recent common ancestry.
Convergent evolvtion occurs as well when
two species from unrelated lines develop the same traits or features
Fossils provide solid evidence that
organisms from the past are not the same as those found today and fossils show a progression of evolution
Anatomy shows the presence of structures in organisms that share the
same basic form as well as the convergence of form in organisms that share similar enviornments
Embryology shows structures that are absent in some groups often appear in their
embryonic forms and disappear by the time the adult or juvenile form is reached
biogeography- the geographic distrubution or organisms on the planet follows patterns that are best explained by evolution in conjunction with the
movement of tectonic plates over geological time
Molecular biology- the structures of molecules
of life reflect descent with modification
Evidence of a common ancestor for all life is reflected in the universality of
DNA as the genetic material and in the near universality of the genetic coder and the machinery of DNA replication and expression
