Post on 05-Jan-2016
Evolution by Means of Natural Selection: The Development of
Adaptations to Survive
Important Vocabulary
1. Fit or Fitness: success at surviving & reproducing
2. Gene Pool: all alleles (forms of genes) shared within a species
3. Frequency: how often an allele is seen in the gene pool a. How does its coloration
help the Snowy Owl survive in its habitat?
b. What other adaptations does it have that makes it “fit” for its environment?
Slide # 2
Coevolution verses Convergent Evolution
Coevolution
1. Two species evolve in response to each other.
2. Examples:
predator/prey
host/parasite species
bees & flowers
Convergent evolution
1. Different lineage, exposed to similar selection pressures
2. Example:
Bats and butterflies. Evolved through different mutations.
3. Convergent evolution produces analogous structures (similar in function, different in structure (bat's wing and butterfly's wing).
a. Variation is inheritable
b. New variations come from mutations in DNA.
c. Some mutations are harmful & some are helpful.
Slide # 4
Requirements for Natural Selection: Variation Exists in Nature
a.Tendency towards overpopulation
b. Strategy for survival: Many species lay tons of eggs; some will survive to adulthood
Slide # 5
Requirements for Natural Selection: More offspring are produced than will survive.
Requirements for Natural Selection: There is a constant struggle for survival.
Slide # 6
a.Competition for limited resources food, space, territory, shelter (nesting sites) & mates
Wolf chasing raccoon
Requirements for Natural Selection: Some individuals in the species will have variations that cause them to be the most fit
in a particular environment.
Slide # 7
a. The fittest individuals will survive the longest & produce more offspring than less “fit” individuals.
b. The most “fit” individuals are best adapted to that particular environment.
c. If environment changes, different variations may be selected to be more fit
Requirements for Natural Selection: Vast amount of time is required for a species to change
Slide # 8
a. After many generations there will be enough genetic change in the population to produce a new species.
Eastern Meadowlark
Western Meadowlark
Separated by a glacier during the last Ice Age, two different species of meadowlark evolved.
Mutations in Genes: the Source of all new Variations
1. Helpful mutations lead to adaptation by increasing fitness & decreasing the death rate• Frequency of helpful mutation
will increase in the population as more individuals survive & leave offspring
2. Harmful mutations decrease fitness of the individual in that environment & cause a higher mortality rate– Frequency of the mutation will
decrease & might or might not disappear from the gene pool
How is the fruit fly on the bottom different
from the fruits above?
Slide # 9
Adaptations of Birds Feet
The woodpecker’s sharp beak allows it to drill into
trees to catch insects.
Helpful Mutations (Adaptations)Slide # 10
Adaptations: A Result of Compromise
An adaptation may work really great for some things (reaching food) , but they may prose a problem for other things (drinking water)
Slide # 12
Camouflage: A Helpful Adaptation1. Camouflage: having a shape / color that blends
in with the environment
2. Difficult for predators to see the prey
Find the green leaf mantid!Find the canyon tree frog!
Slide # 12
Mimicry: Taking Advantage of Another’s Coloration
1. Mimicry: when a harmless individual looks like a similar, harmful (poisonous) individual
2. Predators learn to avoid both
Viceroy: looks poisonous monarch
Monarch is poisonous
Slide # 13