D4.1 - natural selection process (5p)

Question 1

what is the mechanism for driving evolutionary change?

Answer 1

natural selection
- it operates continuously and over billions of years, resulting in the biodiversity of life on Earth

Question 2

what was the paradigm shift of natural selection?

Answer 2

in Darwin’s time it was widely understood that species evolved, but the mechanism was not clear
- Darwin’s theory provided a convincing mechanism and replaced Lamarckism

Question 3

what is a paradigm shift?

Answer 3

happens when scientific activity and experimentation contradicts arguments or theories that experts previously considered unshakable (dogmas)
- the new ideas allow us to think about the phenomenon in a different way

Question 4

why does the evidence supporting natural selection refute Lamarck’s theory of evolution?

Answer 4

characteristics acquired during an individuals life due to environmental factors are not encoded in the base sequence of genes, so are not inherited

Question 5

what is natural selection?

Answer 5

natural selection is a Very Clever Simple Idea:

V - genetic variation due to random mutation

C - competition due to large number of offspring

S - better adapted organisms survive and reproduce

I - future generations inherit this beneficial allele

Question 6

what is the process of evolution by natural selection?

Answer 6

1. genetic variation (in the particular advantageous trait) among members of the same species
   - this can be due to:
   - random mutation
   - meiosis or sexual reproduction
2. intraspecific competition for resources or to withstand selection pressures
   - this can be due to:
   - abiotic factors
   - species tend to produce more offspring than the environment can hold
3. individuals that are better adapted tend to survive and produce more offspring
4. individuals that are less well adapted tend to die or produce fewer offspring
5. inheritance: individuals that reproduce pass on characteristics to their offspring
6. this increases the frequency of the characteristics that make individuals better adapted and decreases the frequency of other characteristics

Question 7

what are 2 ways variation within a population is generated by?

Answer 7

1. mutation - generates new alleles
2. sexual reproduction, which generates new combinations of alleles through crossing over and random assortment during meiosis, and through random fertilisation

Question 8

how does evolution by natural selection depend on mutations?

Answer 8

1. mutation causes variation among organisms of the same species
2. some mutations make individuals more suited to its environment
3. theses individuals that are better adapted survive and produce offspring, passing on advantageous mutation to offspring
4. natural selection increases the frequency of alleles and therefore characteristics that make individuals better adapted

Question 9

what are examples of abiotic factors act as selection pressures?

Answer 9

they are density-independent factors that affect survival of individuals in a population
- temperature
- pH
- salt salinity
- water availability
- oxygen concentrations in aquatic ecosystems

Question 10

what does selection pressure cause?

Answer 10

creates competition, as some individuals have traits that make them better adapted to the abiotic conditions than other individuals

Question 11

what are density-dependent factors that promote natural selection?

Answer 11

• overproduction of offspring
• competition of resources, such as food

Question 12

what determines carrying capacity of an ecosystem?

Answer 12

intraspecific competition, caused by selective pressures, determines the carrying capacity of an ecosystem as only the best adapted individuals survive and reproduce

Question 13

what are density-independent factors?

Answer 13

factors which have the same intensity of impact whether the population is sparse or overcrowded
- weather
- climate change
- natural disasters

Question 14

what are density-dependent factors?

Answer 14

factors which have a larger impact, the more dense the population
- competition for limited resources
- the increased risk of predation
- and the increased transfer of pathogens or pests in dense populations

Question 15

what is natural selection promoted by?

Answer 15

overproduction of offspring and competition for resources, that may limit carrying capacity

Question 16

what is the basis for natural selection?

Answer 16

differences between individuals in adaptation, survival and reproduction

Question 17

what is intraspecific competition?

Answer 17

competition between members of the same species

Question 18

what is a survival value?

Answer 18

adaptations that directly increase the likelihood of an individual’s surviving have ‘survival value’
- this increases the fitness of an organism

Question 19

what is the reproductive potential?

Answer 19

organisms may increase their reproductive potential by producing more offspring, increasing the likelihood that some will reach maturity

Question 20

what is fitness?

Answer 20

ability to withstand the abiotic conditions and obtain sufficient of the limited resources, based on an individual’s genotype

Question 21

what is genetic variation?

Answer 21

different phenotype or differences between individuals in a population / species

Question 22

what is needed for evolutionary change to occur?

Answer 22

the traits must be heritable