Download Evolution Study Guide

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
Evolution – the process of biological change in a species by which descendants come to differ
from their ancestors
o Species – a group of organisms so similar to one another that they can reproduce fertile
offspring
o Population – all the individuals of a species that live in an area

Carolus Linnaeus :
o 1700’s
o Proposed a system of organization of all living things based on physical similarities
o Proposed that organisms might have arisen from crossing between two similar species
 Ex. – a mustang can mate with a miniature horse and produce a pony that an
reproduce because the parents are from the same species; a horse and donkey
can mate but the mule produced will not be fertile

Jean-Baptiste Lamarck :
o 1809
o Believe in decent from common ancestry
o Proposed that organisms have a tendency towards perfection and needed to change to
better fit their environment
o Through selective use and disuse of organs, organisms acquired or lost certain traits
during their lifetime
o By passing on these acquired traits to their offspring, a species can change over time
 Acquired trait – a characteristic which develops in your life time (such as
throwing a baseball far)

Charles Darwin :
o Took 5 year voyage to Galapagos Island
 Noticed tortoises’ difference in shape of shell and how the variations of finches
were suited to their environment and diet
o Theory of Natural Selection :
 In a population there are variations
 Populations tend to overpopulate
 Organisms with the best variation will be better suited to the environment and
survive
 Survival of the fittest :
o Fitness- measure of ability to survive and produce the most
offspring
o Those members of the population with the best natural
variations (adaptations) will survive and pass those traits onto
their offspring

o
Adaption – feature that allows an organism to better
survive in its environment
Fitness is measured in the number of grandchildren someone
has
 Ex. – a person who lives to be 60 with 20 grandchildren
is more fit than a person who lives to be 100 but has no
children
Natural Selection
The environment acts as the selecting agent
o
Artificial Selection
Process where humans change a species by
breeding it for certain traits
Proof of Evolution
 Fossils – trace of an organism that existed in the pasts such as dinosaur
footprints or an imprint in a rock or bones
 The earth is 4.6 billion years old
 Embryology
 Anatomy

Thomas Malthus :
o Stated that whenever a population gets too large, there are limited resources available
to them
o Sooner or later, there will not be enough space, food or water
o War, famine and disease are the only forces to keep the population size from
outdistancing food supply
o Darwin’s theory of natural selection was influenced by this idea

Homologous vs. Analogous Structures
Homologous Structures
Same structures but different functions

Analogous Structures
Have same function but different structure and
occupy the same niche
Vestigial Structure – structures which no longer have a function to an organism
o Ex. Appendix, hair, coccyx, wisdom teeth

Population – all the individuals of the same species in a given area
o ex: You are a population of Biology students in room A46.

Gene Pool – the combined alleles (different form of the gene individuals in a population)

Allele frequency – measure of how common an allele is in the population

Mutation – a random change in the DNA of a gene
o Gene mutations are inheritable if in gamete
o SPONANEOUS
o Recombination – due to meiosis, new combinations of chromosomes and therefore
genes may occur

Factors that can change allele frequency:
1. Gene Flow
 The movement of alleles from one population to another
2. Genetic Drift
 In a small population, a particular allele may occur more or less frequently
even though it was purely due to chance; leads to a loss of variation in a
population
o Ex: Amish population and polydactylism
3. Bottleneck effect
 Effect of a destructive event that leaves a few survivors in a population
(form of Genetic drift)
4. Sexual Selection
 Certain traits increase the likelihood of finding a mate and therefore passing
on genes (fitter)
 Ex: Why the pale peacock is so colorful.
 Reproductive Isolation - occurs when members of different populations can no longer mate
and produce successfully with each other.
 Geographic Isolation – a physical barrier such as a river or mountains, separates two
populations resulting in eventual reproductive isolation.
 Behavioral Isolation – isolation caused by differences in courtship or mating behaviors
o Scents, dances, songs, signals

Coevolution – two totally unrelated species evolve in response to changes in each over time
o Ex: Bees see yellow and blue, thus most bee pollinated flowers are blue and yellow

Gradualism – evolution is a constant process and occurs at a steady rate

Punctuated equilibrium – periods of equilibrium followed by rapid periods of change
o Changes occur with environmental pressures
o Species arise quickly and then have long periods of little change

Convergent evolution – occurs when unrelated organisms occupy the same niche and tend to
have similar characteristics (analogous structures)
o Ex: shark and dolphin

Divergent evolution – closely related species evolved in different directions, becoming
increasingly different
o Ex: dogs share a common ancestry with the wolf.