Chapter 26 - Natural Selection

Question 1

why are all individuals different

Answer 1

inherited different genes –>

Question 2

Explain mutations

Answer 2

origin of genetic variation

occur spontaneously, can be increased by heat, high energy radiation, mutagenic chemicals (environmental factors)

Question 3

Evolution?

Answer 3

changes in a species over time

Question 4

Explain natural selection

Answer 4

Genetic variability in a population
some individuals are better suited to environment = more likely to survive and reproduce
will pass on their advantageous genes for favourable characteristics to their offspring
over many generations = proportion of indivs with favourable genes will be increased and maintained unless environment changes
THIS IS A CHANGE IN SPECIES NOT INDIVIDUAL

indivs are either born better adapted or not –> they do not become adapted

Question 5

Example of natural selection

Answer 5

peppered moth example

Question 6

speciation

Answer 6

the evolution of two of more species from one

Question 7

for speciation to occur:

Answer 7

1. population needs to be split eg a geographical barrier (allopatric speciation) = two separate groups cannot meet = no gene flow
2. in each group the population is made of genetically varied individuals
3. each group has its own environmental conditions, abiotic and biotic factors act as selecting agents = unique populations
4. Time = so different that they cannot interbreed to produce fertile offspring = different species!

plus natural selection!!

Question 8

what is a reproductive isolating mechanism

Answer 8

biological features, stopping organisms from producing fertile offspring with others

Question 9

Prezygotic barriers?

Answer 9

prevents mating or fertilisation

• temporal isolation
• behavioural “
• mechanical “
• gamete “

Question 10

Postzygotic barriers?

Answer 10

prevent the development of fertile adults

• hybrid inviability
• hybrid sterility