Selection And Evolution

Question 1

Explain what is meant by the term species

Answer 1

• Similar physiological features
• Can interbreed to produce fertile offspring
• occupy same niche

Question 2

Explain how speciation occurred questions

Answer 2

• no breeding/ gene flow between populations
• mutations occur
• different selection pressures
• genetic change (different alleles selected for)
• different chromosome numbers
• genetic drift
• allopatric speciation

Question 3

Explain how resistance could have evolved?

Answer 3

Mutation/ random changes
Individuals with mutation more likely to survive
Adults with mutation survive and breed
Mutated gene/ resistant allele passed onto next generation
Increase in frequency of allele for resistance

Question 4

Explain how natural selection reduced the flower size in the flowers

Answer 4

Range of flower size in original population
Genetic variation affecting flower size in original population
Change in environment/ selection pressure in the absence of bees
Plants with small flowers/ petals are selected for/ reproduce
Alleles for small size passed onto offspring
Frequency of advantageous allele increases
Directional selection
Temperature/ space/ competition different in a field and a glasshouse

Question 5

Suggest why there are few predators in the ecosystem even though there are many producers

Answer 5

Predators are secondary consumers
Population size of predators is limited by numbers of prey
Energy loss between trophic levels
Prey numbers small so competition for food
Predators hunted by humans
Habitats destroyed

Question 6

Explain how mosquitos evolved resistance to deltamethrin

Answer 6

Random mutation occurs
Deltamethrin acts as the selection pressure
Resistant mosquitos have the selective advantage
Resistant mosquitos survive and reproduce
Resistant alleles passed on
Increase in frequency of resistance allele