Chapter 13
Evolution & Adaptation
Name ______________________________
Life Science
1. Adaptation – An inherited trait that helps increase an organism’s chance to survive is called
an adaptation. Adaptations include changes to body structure that allow an organism to feed,
move around, and protect itself. (258)
2. Evolution – Evolution is the process of how organisms acquire adaptations over time that
allow them to survive. (258)
3. Diversity – There is a great variety of living things on this planet. This is called diversity.
Scientists believe there are between 5 and 50 million different species of organisms. They
hypothesize that all species come from a common ancestor and new species simply branch off
from earlier species. (259)
4. Ancestor – An ancestor is an organism from which others have descended. All living things
are made of cells and all cells have many similarities (cell membranes, same types of cellular
respiration, & DNA). These similarities at the cellular level between all cells support the
hypothesis that all life evolved from common ancestry. (259)
5. Cladogram – A cladogram illustrates evolutionary relationships among living species and
their ancestors. (259)
6. Lines of Evidence – There are three lines of evidence that support the theory of evolution:
comparative anatomy, DNA analysis, and the fossil record. (261)
7. Comparative Anatomy – Comparative anatomy is the study of anatomical similarities and
differences among different species. (261)
8. Homologous Structures – Body structures in different species that have a common origin do
not always perform the same function. These are called homologous structures (arm, wing,
fin, leg). (261)
9. Analogous Structures – Structures in different species that evolved separately but perform
the same function are called analogous structures (wing of a bird, wing of an insect). (261)
10. Vertebrates – Animals that have a backbone are called vertebrates (mammals, birds,
reptiles, amphibians, and bony fish). This again is evidence that we all descended from a
common ancestor. (262)
11. DNA Analysis – In DNA analysis species that share more similarities in their DNA base
sequences are more closely related than those that don’t. (262)
12. Fossil – A remnant or trace of an organism from the past is called a fossil. This can include a
skeleton or leaf imprint embedded and preserved in the Earth’s crust. Fossils offer clues to
evolutionary history. (263)
13. Sedimentary Rock – Sedimentary rock is formed from layers of sediment like sand, mud,
tiny shells, or small rocks. Over long periods of time more and more layers pile up on one
another. This compresses them into rock. Sedimentary rock often has fossils in it. The farther
down the layer the older the rock and the fossil. (263)
14. Fossil Record – An historical sequence of life on earth, based on the sequence of fossils in
different layers of rock, gives us what is called the fossil record. Not all species fossilized
so there are gaps in the fossil record. (264)
15. Charles Darwin – In 1859 Charles Darwin published a book on the origin of all species by
means of natural selection. He concluded four main things. 1. Organisms change over time.
2. All organisms are descended from common ancestors by the process of branching.
3. Evolution is gradual and takes place over a long period of time. 4. The mechanism of
evolution is natural selection. (268)
16. Natural Selection – Darwin believed that organisms with favorable adaptations (traits)
survive and reproduce at a higher rate than organisms with less than favorable adaptations.
This is called natural selection. There are four ideas behind natural selection. 1. All
populations over-reproduce. 2. Individual organisms in a population vary. 3. Favorable
adaptations are selected. 4. Favorable adaptations accumulate. (269)
17. Genetic Variation – The variety of gene alleles in a population is called genetic variation.
Genetic variation is necessary for natural selection. The greater the genetic variation in a
population the better chance of survival there will be should the environment change. (272)
18. Species – An isolated population of similar organisms that can interbreed and produce fertile
offspring is called a species (tigers, bald eagles, lions, pine trees, rainbow trout). A new
species evolves in three steps. 1. Isolation: A part of a population gets divided from the
group by an event such as a volcano, flood, earthquake, etc. They become physically and
reproductively isolated from the others. 2. Adaptation: If the isolated population goes
through environment change then new adaptations happen due to natural selection. This
makes them different from the original population. 3. Species Formation: If the isolated
group becomes so different from the other group that they can no longer interbreed a new
species has formed. (273)
19. Extinction – When the adaptations a population makes do not happen quickly enough, or
they are not sufficient for survival, the population dies out and becomes extinct. (274)