7 Genetics & Ecosystems- Evolution

Question 1

What is phenotypic variation and what is it caused by?

Answer 1

-visible differences in characteristics between individuals
-caused by a combination of genetic variation & the environment

Question 2

What is genetic variation and how does it happen?

Answer 2

-Variation caused by the genetic code
-Happens when individuals of the same species have different alleles

Question 3

What is environmental variation and what is it caused by?

Answer 3

-Environmental factors contribute to phenotypic variation
-Genotype of an individual interacting with the environment

Question 4

What are the causes of genetic variation + explain?

Answer 4

-Mutation; changes in base sequence, may cause structure of proteins encoded by DNA to alter. Can be harmful/beneficial/no effect on survival
-Recombination; In meiosis, genes on homologous chromosomes are reshuffled in recombination/crossing over, makes new combinations of genes
-Independent segregation; Homologous chromosomes are randomly separated into haploid cells in meiosis
-Random fertilisation; gametes of 2 unrelated individuals are fused in sexual reproduction to produce a diploid individual.

Question 5

What are the factors influencing whether an individual is capable of surviving?

Answer 5

-Predation; high= more likely to be eaten by predator. An individual better at avoiding predators= more likely to survive & reproduce, genes allowing individual to avoid predation more likely to be passed onto offspring
-Disease; individual better at combatting disease/avoiding infection= more likely to survive & reproduce. Genes allowing individual to avoid disease= more likely to be passed onto offspring
-Competition; exist between species (interspecific)/within species (intraspecific) If individual is better at outcompeting other individuals= more likely to survive & reproduce. Genes allowing individual to outcompete= more likely to be passed onto offspring

Question 6

What is natural selection and what does it give rise to?

Answer 6

-The process where frequency of alleles in population changes over time
-Gives rise to evolution
-If a harmful allele develops in an individual, this individual= less likely to survive & harmful allele will decrease in frequency

Question 7

What is a selective advantage and what does it cause?

Answer 7

-Some individuals are more likely to survive than others due to genetic variation
-These individuals have a selective advantage and are more likely to reproduce and pass this on to offspring
-Allelic frequency providing a selective advantage increase

Question 8

What is evolution defined by?

Answer 8

A change in allele frequencies over time

Question 9

What is a selection pressure and why is it imposed?

Answer 9

-An external factor influencing reproductive success of an individual
-Natural selection acts on an individual by imposing a selection pressure

Question 10

What is stabilising selection and where does it take place?

Answer 10

-Natural selection favours an average phenotype
-Selection pressure select against the extreme phenotypes
-Take place in environments that do NOT change

Question 11

What is directional selection and where does it take place?

Answer 11

-Natural selection favours one extreme phenotype
-Selection pressures in directional selection select against all other phenotypes.
-Takes place after an environment has experienced a change

Question 12

What is disruptive selection and what can it lead to?

Answer 12

-Natural selection favours two extremes of a phenotype
-Selection pressures select against average phenotype
-Takes place in an environment that favours more than one phenotype
-Can eventually lead to production of 2 new species

Question 13

What is speciation?

Answer 13

Where 2 new species arise from a single species

Question 14

What is the process of speciation occurring?

Answer 14

-Reproductive isolation; two populations are prevented from interbreeding & differences accumulate in the two gene pools. The gene flow (movement of alleles between population) of the populations is restricted
-As genetic differences accumulate, the two populations can no longer interbreed to produce fertile offspring; are separate species

Question 15

What is allopatric speciation?

Answer 15

Where two or more populations are geographically (physically) isolated from each other; via environmental change like the emergence of a river or random events like a storm carrying birds to another island

Question 16

What is the process of allopatric speciation occurring?

Answer 16

-Populations of a species can split into two or more through geographical isolation (enviro/random)
-Populations in diff environments will be exposed to diff environmental conditions (climate, food)
-This will place diff selection pressures on the populations; they’ll drive natural selection in diff directions
-diff selection pressures on populations—> allele frequencies in the populations change
-If populations continue to be geographically isolated for long time, eventually allele frequencies will change so much that if they’re brought back together they can no longer interbreed= now considered two diff species

Question 17

What is sympatric speciation?

Answer 17

Where two or more populations aren’t geographically isolated from each other; may arise when mutation emerges preventing members from interbreeding w/ others

Question 18

What is the process of sympatric speciation occurring?

Answer 18

-A population of species is reproductively isolated w/ out geographical (eg via mutation)
-The mutations influence many diff factors; eg polyploidy (extra set of chromosomes causing them to be reproductively isolated from diploid organisms), flowering/mating times of individuals, altering reproductive organs & mating behaviours
-The emergence of a mutation prevents two (or more) populations from interbreeding, eventually will no longer be able to create fertile offspring and will be 2 diff species

Question 19

What is genetic drift and what can it drive?

Answer 19

-The random change in allele frequencies in a population
-Can drive speciation

Question 20

What is genetic drift and how does it contribute to speciation?

Answer 20

-By chance, some alleles—> passed onto offspring, some aren’t
-Causes random changes in allele frequencies in population.
-Contributes to speciation by causing random changes in allele frequencies of two populations
-As the two populations can no longer interbreed, gene pools will become increasingly different; causes speciation
-Tends to have larger influence on evolutionary change in smaller populations as gene pool= smaller, so any change in allele frequencies has larger impact on overall gene pool

Question 21

How are speciation and evolution important for diversity of life?

Answer 21

-Speciation= process that led to huge diversity of species that exist in life today; every species originally stemmed from a single population
-New species can emerge via speciation due to -evolution; as two populations—> reproductively isolated, natural selection causes separate populations to evolve in diff directions
-continuous cycle of evolution & speciation is what has led to the diversity we see today