5.2 Natural Selection

Question 1

Conditions for Natural Selection

Answer 1

Variation in characteristics of individuals

Heredity of characteristics

Reproduction of more offspring than the environment can support

Variation in fitness (ability of an organism to survive and reproduce)

Question 2

Variation is typical in natural populations and means

Answer 2

individuals differ in their traits

Question 3

The implication of variation is that some individuals will be more suited to particular conditions and hence

Answer 3

more likely to survive.

Question 4

Species that only carry out asexual reproduction can only rely on _____________ for variation

Answer 4

mutation

Question 5

variation between members of a species is due to

Answer 5

random mutation
- DNA rep
- viral infection

sexual reproduction
- meiosis
- crossing over In prophase 1
- random assortment of chromosomes in metaphase 1
- random fertilisation

Question 6

In biology, the relationship between structure and function is important to study

Answer 6

E.g. the structure of a bird’s beak is correlated with its diet and method of feeding

Question 7

Structures/characteristics that make an individual suited to its environment or way of life are called

Answer 7

adaptations

Question 8

Adaptations take time to develop and are a result of

Answer 8

natural selection

Question 9

Adaptations do not develop during an individual’s lifetime,

Answer 9

individuals are born with these traits as a result of the DNA

Question 10

Characteristics that do develop during an individual’s lifetime are called acquired characteristics:

Answer 10

these cannot be inherited and do not contribute to evolution
e.g. scars, dyed hair, tanned skin (not based in genes)

Question 11

In general, organisms produce more offspring than the environment can support:

Answer 11

Darwin suggested that this will increase competition and not every individual will obtain enough to allow them to survive and reproduce

Question 12

struggle for survival

Answer 12

• competition for food
• predation
• paratism
• disease
• competition for mates
• competition for space

Question 13

Traits that give an advantage are selected for

Answer 13

A mutation/trait that causes an individual to be better suited to the environment will survive and reproduce and pass on the trait to future generations (many offspring)

Question 14

Traits that give a disadvantage are selected against

Answer 14

A mutation or trait that causes an individual to be worse suited to the environment will not survive and therefore not be able to pass on the trait to future generations (few offspring)

Question 15

This leads to an increase in the proportion of individuals in a population with characteristics that make them

Answer 15

well-adapted

Question 16

Over many generations, the characteristics of the population will gradually change –

Answer 16

this is evolution by natural selection

Question 17

Alleles that encode for well adapted characteristics increase in frequency

Answer 17

whilst those that encode for ill adapted characteristics decrease

Question 18

Darwin studied finches on the Galapagos Islands in 1835 – there are 14 species

Answer 18

He observed that the beaks of finches varied and so did their diet

Darwin hypothesized that the finches had originated from one species which had evolved into many different species on the different islands

Each new island had different selective pressures, so over millions of years, the finches adapted to better suit their own islands. Eventually they became separate species.

This is know as adaptive radiation

Question 19

The Grants documented the changes in beak length as a result of changing weather conditions

Answer 19

Changing weather affects the types of seeds that grow (plentiful small seeds during wet years, shortage during dry years)

These finches provide support that significant changes can occur in populations via natural selection

Question 20

Antibiotic resistance in bacteria is due to genes so can be inherited
This means that populations of bacteria can

Answer 20

evolve to become resistant to antibiotics

Question 21

evolution of antibiotic-resistant bacteria

Answer 21

non-resistant strains of bacteria die and resistant strain survives

genes for resistant to antibiotics gets passed on

resistant population grows

Question 22

Antibiotic resistance in bacteria can evolve very quickly…

Answer 22

Widespread use of antibiotics

Bacteria can reproduce rapidly

Populations of bacteria are huge, meaning the antibiotic resistant gene has a higher chance of occurring via mutation

Bacteria can pass genes onto other bacteria in many ways, including plasmids