Biodiversity: Adaptation and Evolution (Solving problems using Hardy…
Adaptation and Evolution
Key words and Definitions
Ecology: the study of living things within their environment. This is an essential part of modern biology.
Ecosystem: a community of organnisms and their surroundings, the environment in which they live e.g. woodlands
Habitat: the place an organism lives.
Niche: The way in which an organism exploits its environment
every species has a unique niche
Where niches overlap, competition results.
where niches are identical, one species will out compete the other causing extinction.
Natural selection: natural selection is the process by which organisms are able to become adapted to their environment. It is dependent on variation.
Evolution: A change in allele frequency over time (where allele feequency is the proportion of one allele in a population.
Adaptability of a population depends on: size of selection pressure, size of gene pool and reproductive rate of organisms
Phenotypic variation exists within populations because of crossing over, independent assortment of chromosomes and mutation. This results in a larger gene pool
More organisms are borne than can survive so the population decreases due to depredation, disease (creating selection pressures which cause a struggle for survival)
The better adapted individuals are more likely to survive and therefore reproduce and pass on their advantageous alleles>
The proportion of the population with the advantageous alleles increases through the generations.
As the frequency of alleles is changing the population is evolving.
Solving problems using Hardy-Weinberg
If 98 out of 200 individuals in a population express the recessive phenotype, what percent of the population would you predict would be heterozygotes?
p + q = 1 (this cannot be used directly so use pxp + 2xpxq + qxq
q squared = 98/200
q squared = 0.49
q = 0.7
p = 1-0.7
p = 0.3
2pq = 2(0.3)(0.7)
so 2pq = 0.42 or 42% of the population are heterozygous
The waxy leaf frog is a species of frog found in hot, dry areas of South America. It has glands that produce waxy lipids to spread over its skin. This reduces water loss the waxy leaf frog is active only at night, when it hunts for insects in the trees. Suggest how natural selection could have given rise to the adaptations shown by the waxy leaf frog?
/ change in environment / hot and dry habitat (1)
competition / predation
Mutation (in frog) (1)
e.g. allele for waxy secretions (1)
Idea that individuals with
advantageous alleles / characteristics
survive and breed (1)
advantageous allele / mutation
being passed on to future generations (1)
Increased frequency of advantageous alleles in the population (1)
With reference to the waxy leaf frog, explain what is meant by the term niche.
Idea that it eats insects
at night / in trees
Within the community / ecosystem / habitat / environment
/ hot dry areas (1)
Forming a new species
Forming a new species requires reproductive isolation
Occurs when part of a population is no longer able to interbreed with the rest of the population
Typically a result of a geographical feature such as a mountain range or an ocean which physically separates a population
Divergent evolution may begin as the group accumulates.