7F: Mechanisms of Evolution

Mechanisms of Evolution

Evolution

● Change in the gene pool of a population from generation to

generation by processes such as small populations, non-random
mating, mutations, gene flow, and natural selection

Multiple Choice

Which combination of characteristics in a population would provide the greatest potential for evolutionary change?

• Small population, low mutations rates

• Large population, low mutation rates

• Small population, high mutation rates

• Large population, high mutation rates

Gene pool

●

The set of all genes, or genetic information, in any
population, usually of a particular species

Mechanisms of Evolution (ways evolution occurs)

1.

Small population

2.

Non-random mating

3.

Mutations

4.

Gene flow

5.

Natural selection

1. Small Population

●

Genetic drift

●

Random chance can cause alleles to disappear
easily

●

This would change the allele frequency

●

EX: Random event (flood, forest fire, deforestation
etc.)

Genetic Drift

●

Change in allele frequency due to random chance event

●

Forces remaining population to evolve !!

●

Leads to low genetic diversity

Multiple Choice

During a hurricane, a population of beetles almost gets completely wiped out. The only beetles that survived were lucky that they were in their nest at the time of the hurricane and had enough food to survive.

• Natural selection

• Genetic Drift

  (small population)

• Gene Flow

• Non-Random Mating

Multiple Choice

A certain type of plant can produce blue or yellow flowers. During a fire, many yellow flowers are destroyed and now since blue is the dominant trait, the plant reproduces offspring that produce only blue flowers.

• Non-Random Mating

• Gene Flow

• Mutation

• Genetic Drift

  (small popluation)

2. Non-Random Mating

●When animals pick partners based on those similar
to them

●The females choose which males they’ll mate with

●When animals pick partners based on location

●Ex: Blue Footed Bobys; females choose which male
to mate with based on best dance courtship behavior

Multiple Choice

Males of the bighorn sheep species fight one another to show females who is the dominant male and are more likely to mate with females.

• Natural Selection

• Mutation

• Genetic Drift (small population)

• Non-Random Mating

Multiple Choice

Females a certain bird species are attracted to the mating calls of male species more than others

• Genetic Drift

  (small popluation)

• Mutation

• Non-Random

• Natural Selection

3. Mutations

●

New traits from mutations change the gene
pool

●

Ex: Eye pigment color, hair color, height,
metabolism ect.

●

Increase genetic diversity !

Multiple Choice

A chemical spill causes the offspring of ladybugs to have blue dots instead of black dots.

• Natural Selection

• Genetic Drift (small population)

• Mutation

• Gene Flow

Multiple Choice

Some organisms of a population of birds are born with extra-long beaks instead of a normal sized beak.

• Gene Flow

• Natural Selection

• Genetic Drift

  (small population)

• Mutation

4. Gene Flow

●

Movement of genes into a population

●

Caused by immigration (in) or emigration (out)

★

Increases genetic diversity

Multiple Choice

7F: Common baboons live on the savanna in breeding groups called troops. While females tend to stay with the troop, younger or less dominant males may leave to join a neighboring troop. Which of these is a likely outcome of movement by young males?

• Gene flow occurs between population

• Allele frequencies suddenly change

• Relative genotypic frequencies reach a constant state

• Intermediate phenotypes increase in the species

Multiple Choice

7F Two populations of mice living in the same forest are separated by a large water-filled ditch. After a rainstorm, flooding brings several mice from one population to the other population. When the mice from the first population reproduce with members of the second population, which of the following will likely occur?

• All the offspring will die as a result of reproductive mutations

• The offspring will be forced to leave the second population.

• The offspring will be genetically identical to their parent from the first population.

• The offspring in the second population will have greater genetic variety

Multiple Choice

7F Lord Howe Island is a volcanic island in the Tasman Sea that is about 11 km long and 2.8 km wide. The island has two species of palm trees, Howea forsteriana and the more abundant Howea belmoreana. The two species do not interbreed even when they grow very close to each other. Which evolutionary process fails to occur?

• Genetic drift of Howea forsteriana

• Natural selection of adaptive traits in both species

• Gene flow between the two species

• Mutations in Howea belmoreana

Multiple Choice

Reindeer from a rancher in Alaska escape from their pen during an enormous snow storm. After their escape, they mate with wild caribou that are migrating across the land. The offspring of these have traits for short legs and have tame behavior.

• Gene Flow

• Genetic Drift (small population)

• Non-Random Mating

• Natural Selection

Multiple Choice

The country of Sweden is known for having people with blonde hair and blue eyes. One day a family moves from Sweden to India where dark hair and dark eyes are very common. A female from Sweden marries a male from India and their offspring now have blonde hair and blue eyed traits.

• Natural Selection

• Mutation

• Non-Random Mating

• Gene Flow

5.Natural Selection

●

“ONLY” “finger” that leads to
ADAPTATION

●

Creates organisms better adapted for
their environment

If it helps an organism:

1. Live longer
● Find food
● Not get eaten
● Stay warm/keep cool
2. Pass on its genes
● Find a mate
● Protect offspring

IT’S AN ADAPTATION

Adaptations are ALWAYS good !!!= SURVIVAL

Multiple Choice

Insects become resistant to pesticides very quickly, sometime in one generation. If an insect is resistant to the chemical, most of the offspring will also be resistant. Considering that insect generations can be a matter of weeks, insects in an area can become immune to a chemical within months.

• Mutation

• Natural Selection

• Genetic Drift

  (small population)

• Gene Flow

Multiple Choice

In a habitat there are red bugs and green bugs. The birds prefer the taste of the red bugs, so soon there are many green bugs and few red bugs. The green bugs reproduce and make more green bugs and eventually there are no more red bugs

• Genetic Drift

  (small population)

• Natural Selection

• Gene Flow

• Mutation

Multiple Choice

Bats are common in Texas, especially in rocky regions. Bats with longer hang claws have demonstrated higher fitness because of their ability to cling to rock while resting.

• Adaptation

• Non-random mating

• Gene Flow

• Mutation

Microevolution

●

Evolution on a very short time scale

●

“Micro” means small

Macroevolution

●

Evolution on a long time scale,involves speciation

●

“Macro” means large