Natural Selection/Evolution

Question 1

Evolution

Answer 1

The changes in inherited traits in a populations over time

Question 2

Microevolution

Answer 2

The small changes within a population or species. These occur over a relatively short period of time within a population’s gene pool.

Question 3

Macroevolution

Answer 3

The large changes in evolution over a relatively long period of time

Question 4

Charles Darwin

Answer 4

→ He debunked a lot of leading theories at the time. He proved that…
↪ Species can change over time (it was believed that they were fixed)
↪ Earth was a lot older than previously mentioned - so evolution was possible with the age of the Earth

→ His biggest was the Theory of Natural Evolution that he and Alfred Wallace had developed (Though Darwin did write a 502 page book called “The origin of species”)

Question 5

Gene Pool

Answer 5

The total collection of genes (alleles) in a population at any one time. (Think of it as a reservoir that the next generation can use to get their genes)

You can quantify a gene pool by measuring allele frequency.
↪ We can measure the evolution as a change in the prevalence of a certain heritable trait in a population over a succession of time.

Question 6

Population

Answer 6

A group of individuals of the same species living in the same place at the same time. It is the smallest unit that can evolve.

AN INDIVIDUAL CANNOT EVOLVE.

Question 7

Factors the drive Microevolution

Answer 7

→ Non-Random Changes
↪ Natural Selection
↪ Artificial Selection
↪ Sexual Selection

→ Random Changes
↪ Mutations
↪ Genetic Drift
↪ Gene Flow

Question 8

Natural Selection

Answer 8

→ The main concept is the “survival of the fittest”
↪ “fit” doesn’t necessarily mean fastest or strongest (it could - but not all the time)
↪ Not fit means they won’t (likely) survive or reproduce in the environments that they live in, meaning they won’t pass on the trait
↪ Survival is NOT Random
↪ Individuals that survive and reproduce do so because their genetic makeup is suited (more fit) for the environment that they inhabit

Question 9

Survival of the Fittest

Answer 9

How well an individual will survive and reproduce.

Question 10

The 4 Criteria of Natural Selection

Answer 10

1) Variation: There is pre-existing variation in a population.
2) Competition/Struggle: Called Selective Pressure, any reason a phenotype has an advantage over the other.
3) Environmental Selection: Environment selects fit variant (fitness = survival to reproduction).
4) Reproduction and Inheritance: The Variation is passed on to the next generation.

Question 11

Adaptations

Answer 11

The result of natural selection in a population or species is adaptation.
↪ An adaptation is a feature or a trait that a species has that makes it more fit (better suited to survive and reproduce) in its environment.
↪ They make animals more likely to survive

→ There are three types of Adaptations
↪ Structural (Physical Features)
↪ Behavioral (The way an individual acts)
↪ Physiological (Internal body processes of an organism)
→→ Most species have a combination of all three adaptations

Question 12

Animals compete for

Answer 12

→ Nutrients
→ Water
→ Protection against weather
→ Not being eaten by predators
→ Fighting against disease
→ Space
→ To reproduce

Question 13

Structural Adaptations (3 Types)

Answer 13

Anatomical…
Anatomical changes in the shape of particular features, either internal or external, that help improve survival.
Ex. Arrangement of teeth, shape of fins or beaks, long digestive tract of herbivores

Mimicry…
Allows one species to resemble another.
Ex. Mimic Octopus

Cryptic Colouration…
Makes potential prey hard to spot using camouflage (blends in with environment).
Ex. A sea horse called a sea dragon looks like the algae in which it lives

Question 14

Physiological Adaptations

Answer 14

Changes associated with the biochemical functions inside an organism.

Ex. enzymes for blood clotting, chemical defenses of plants, silk for silk worm cocoons and spider webs, antibiotic resistance in bacteria

Question 15

Behavioral Adaptations

Answer 15

Associated with how organisms respond to their environments

Ex: migrations, courtship, foraging behavior, response of plants towards light

Question 16

Evidence for Evolution

Answer 16

1) Fossils
2) Selective breeding
3) Evidence of homologous structures.

Question 17

Sources of variation

Answer 17

Mutation
→ New alleles are produced by gene mutation which adds more to the gene pool

Meiosis
→ Produces a new combination of alleles by breeding existing alleles in cells. Processes like crossing over, recombination and independent assortment

Sexual Reproduction
→ Fusion of male and female gametes (two different individual gene pools combining)

Question 18

2 Types of evolution

Answer 18

1) Convergent Evolution: Species evolved to have similar characteristics because of same environment (same selective pressures)
2) Divergent Evolution: Populations with common ancestors that becomes different species. They have homologous structures

Question 19

Homologous Structure

Answer 19

Similar physical features that share a common ancestor but serve different functions.
Ex: Pentadactyl Limb

Question 20

Stabilizing Selection

Answer 20

→ Selection against individuals exhibiting variations in a trait that deviate from the current population average
→ Occurs where the most common phenotypes within a population are most favored by the environment
→ Most common form of selection

Natural selection eliminates extreme variations of a particular trait
→ For example, a hummingbird draws nectar from flowers with the long bill and tongue
→ Species will succeed if bill and tongue length adapted for size of flowers they feed on

Question 21

Directional Selection

Answer 21

When the environment favors individuals with more extreme variations.

→ Often occurs when there is a sudden change in the environment
→ The result of this type of selection is a shift in the population’s genetic variance toward the new, fit phenotype.

Ex. Peppered Moth going from a white phenotypic majority to a black phenotypic majority after the industrial revolution

Question 22

Disruptive Selection

Answer 22

Favors the individuals with variations at opposite extremes of a trait over individuals with an intermediate variation.

→ Environmental changes may favour more than one phenotype
→ The result of this type of selection is increased genetic variance as the population becomes more diverse.

Ex. In squirrels short tails help stop predators from catching them while long tails help them balance in trees. Medium tails are not useful. So two extremes are selected for.

Question 23

Genetic Variation

Answer 23

→ Species that possess a greater number of chromosomes/genes have the potential for increased genetic diversity

→ Similarly, the greater the number of different alleles for these genes, the greater the extent of genetic variation there will be within a species and from individual to individual

→ Genetic diversity within a population increases enormously through sexual reproduction, as the various alleles from two parents recombine in each offspring (crossing over and random assortment)

Question 24

Heterozygote Advantage

Answer 24

The heterozygous geno/phenotype has a higher evolutionary fitness than either homozygous geno/phenotypes.

For example: Sickle cell anemia is a recessive trait that has some effects in heterozygous individuals for the trait. Because of this half-effect these individuals are less susceptible to malaria as malaria invades the red-blood cells but due the affected hemogolbin in the RBC the malaria parasite cannot affect the cell fully and the immune system can clear the cell. This means fewer parasites and a milder illness.

Question 25

Pseudogenes

Answer 25

A DNA sequences that resembles a gene sequence that has mutated to be inactive over the course of evolution

Question 26

Ecological Niche

Answer 26

In ecology, the term “niche” describes the role an organism plays in a community. A species’ niche encompasses both the physical and environmental conditions it requires (like temperature or terrain) and the interactions it has with other species (like predation or competition).

Question 27

Lineages

Answer 27

Lineages are sequences of biological entities connected by ancestry-descent relationships.