Unit 2 KA 2 ✓ Flashcards
Organisms and Evolution (23 cards)
What is Evolution?
Evolution is the change over time in the proportion of individuals in a population differing in one or more inherited traits
What are Selection pressures?
Selection pressures are environmental conditions that can influence which individuals in a population pass on their alleles
What are Biotic selection pressures?
Biotic selection pressures are living factors like competition, predation, disease or parasitsm
What are Abiotic selection pressures?
Abiotic selection pressures are non-living factors like a change in temperature, light, humidity, pH or salinity
Non-random evolution -
What is Natural selection?
Natural selection acts on the genetic variation within a population. It increases the frequency of alleles that improve an organisms chance of survival, and decreases the frequency or deleterious alleles
Non-random evolution -
What is Sexual selection?
Sexual selection is a form of natural selection where the increase in allele frequency is determined through the selection of mating partners
What is Sexual Dimorphism?
Sexual dimorphism is when special features (physical or behavioural) develop in males which differ from females as a result of selection for mates
Sexual selection:
What is Male-male rivalry?
Male-male rivalry is when large size or weaponry increases a males access to females through conflict
e.g. Stags with big antlers, access female deer
Sexual selection:
What is Female choice?
Female choice is when the female assesses the fitness of males
e.g. A more impressive peacock tail will be chosen by the peahen
Random evolution -
What is Genetic drift?
Genetic drift leads to variation in the relative frequency of different genotypes in a population when chance events cause unpredictable fluctuations in allele frequency from one generation to the next, certain alleles may be under represented and others over represented.
NOTE: Small populations are paricularly at risk of losing alleles
Genetic drift:
What is a Population bottleneck?
A population bottleneck is an event that drastically reduces the size of a population for at least one generation. It may be caused by a disaster, over-hunting or habitat destruction. This reduces the gene pool as allele types are lost and the population is left with reduced genetic diversity
Genetic drift:
What is the Founder effect
The founder effect occurs through the isolation of a few members of a population from a larger population. The gene pool of the new population is not representative of the original gene pool
What is the Hardy-Weinburg principle?
(HW principle)
The Hardy-Weinburg principle states that in the absence of evolutionary influences allele and genotype frequnecies in a population will remain constant over the generations
What are the 5 conditions maintaining the HW principle
1) No selection
2) No mutation
3) No migration
4) Large population
5) Random mating
What does the term Fitness mean?
Fitness is a measure of the tendancy of some organisms to produce more surviving offspring than competing members of the same species
In terms of fitness:
What is Absolute fitness?
Absolute fitness is the ratio between frequencies of a particular genotype before and after selection
NOTE: From generation -> generation
In terms of fitness:
What is Relative fitness?
Relative fitness is the ratio between the surviving offspring of one genotype compared to other genotypes
What is Co-evolution?
Co-evolution is the process by which two or more species evolve in response to selection pressures imposed by each other.
A change in traits of one species acts as a selection pressure to the other
What is Symbiosis?
Symbiosis is co-evolved intimate relationships between members of two different species
Symbiotic interaction (1/3):
What is Mutualism?
Mutualism is when both organisms in the interaction are interdependant on each other for resources/services.
Both organisms benefit (+/+)
e.g. Clown fish (protection) and anemone (nutrients)
Symbiotic interaction (2/3):
What is Commensalism?
Commensalism is when only one organism in the interaction benefits but the other organism is not negatively affected.
One organism benefits, other not affected (+/o)
e.g. Birds nesting (protection) in a tree (not affected)
Symbiotic interation (3/3):
What is Parasitsm?
Parasitsm is when the parasite benefits in terms of energy and nutrients, but the host is harmed as a result of a loss of resources.
One organism benefits, the other is harmed (+/-)
e.g. Human (loss of blood) and a leech (gains nutrients)
What is the Red queen hypothesis?
The red queen hypothesis states that in a co-evolutionary relationship, a change in the traits of one species acts as a selection pressure on the other species. Therefore, both species must adapt in order to avoid extinction
