Lecture 12 & 13

General Ecology

Natural Selection Definition:

Differential survival and reproduction of organisms based on their phenotypes

Traits that improve survival/reproduction become _____ over time

more common

Traits that reduce fitness become ______ over time

less common

Natural selection results in _____ contribution of allele to next generation

unequal

Individuals with favorable alleles tend to leave for _______

offspring

Allele Frequency Definition:

how common an allele is in the next generation compared to others

High Fitness:

more common in next generation

Low Fitness:

less common in next generation

Organismal Fitness Definition:

number of offspring produced by individuals with a specific genotype compared to other

What is an example of organismal fitness in the medical field?

Sickle-cell anemia

In terms of sickle-cell anemia, HH =

normal

In terms of sickle-cell anemia, Hh =

slightly anemic

In terms of sickle-cell anemia, hh =

lethal

Sickle Cell Anemia affects the susceptibility to _______

malaria

In terms of sickle-cell anemia, homozygous recessive =

severe SCA, short lifespan

In terms of sickle-cell anemia, homozygous dominant =

normal blood cells, susceptible to malaria

In terms of sickle-cell anemia, heterozygous =

carriers (sometimes anemic), more resistant to malaria

In regions with high malaria presence (Africa), ______ individuals have a survival advantage

heterozygous

In areas with little malaria risk, ________ individuals would have the advantage since they would have no risk of SCA or passing traits down to offspring

homozygous dominant

Natural selection can maintain _______ alleles if they confer an advantage in certain environments

harmful

Will q ever go to zero?

No, theoretically some will always be present in heterozygotes

Are all dominant alleles harmful?

No, some are, not all

What is an example of a dominant allele being harmful?

Huntington’s Disease

Inherent Variation:

Natural Definition

What are the types of Inherent Variation?

Genetics

Upbringing

What are the types of environmental influences for inherent variation?

Nutrition

Learned Behavior

Parental Care / Social Environment

What are the sources of genetic variation?

Genetic Recombination

Mutation

Horizontal Gene Transfer

When does genetic recombination occur?

meiosis

What is horizontal gene transfer?

transfer of genes between unrelated organisms

What type of organism is horizontal gene transfer most seen in?

Bacteria

Horizontal Gene Transfer introduces new genes_____

rapidly

What does higher fitness mean?

better at overcoming limits

What are the types of overcoming limits in terms of individual fitness?

Predator Avoidance

Food Access

Acquiring Mates

Predator Avoidance:

better camouflage, speed, defenses

Food Access:

efficient foraging, competition skills

Sexual Selection Definition:

Type of natural selection that occurs when individuals vary in their ability to obtain or attract mates, and these differences affect reproductive success

Altruism Definition:

form of natural selection where the behavior that reduces their own fitness, but increases the fitness of a relative

When is altruism favored?

When cost to one is less than the benefit to another

According to Hamilton’s Rule, an individual should take up to ___ chance of dying to prevent death of: sibling, parent, child

50%

According to Hamilton’s Rule, an individual should take up to ___ chance of dying to prevent death of: grandparent, cousin, niece, aunt

25%

What organism is altruism commonly seen in?

Honeybees

What are the types of selection?

stabilizing

directional

disruptive

In stabilizing selection, the selection is:

against both extremes

Stabilizing selection favors individuals with _______ traits

intermediate

Stabilizing selection _____ trait variation, but maintains average

reduces

Stabilizing selection is common in _______ environments

stable

In directional selection, the selection is:

against one extreme

Directional selection shifts population towards:

the other extreme

Directional selection is often seen in _______ environments

changing

Disruption Selection is also known as

Diversifying selection

In disruptive selection, the selection is:

against the average

Disruptive selection favors individuals…

at both extremes

Disruptive selection can ______ variation

increase

Disruptive selection may lead to the formation of:

subpopulations or even speciation