D4.1 - natural selection

Question 1

Lamarckism

Answer 1

A theory of evolution that states that organisms can pass on physical characteristics to their offspring that they acquired during their lifetime

Question 2

What is the mechanism for driving evolutionary change?

Answer 2

Natural selection
- It operates continuously and over billions of years, resulting in the biodiversity of life on Earth.

Question 3

What was the paradigm shift of natural selection?

Answer 3

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 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 a paradigm shift?

Answer 5

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 6

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

Answer 6

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 7

How does evolution by natural selection depend on mutations?

Answer 7

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 8

What are examples of abiotic factors act as selection pressures?

Answer 8

They are density-independent factors that affect survival of individuals in a population.
- Temperature
- pH
- Water availability
- Salinity
- Oxygen concentrations in aquatic ecosystems

Question 9

What does selection pressure cause?

Answer 9

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

Question 10

What are density-dependent factors that promote natural selection?

Answer 10

• Overproduction of offspring.
• Competition of resources, such as food.

Question 11

What determines carrying capacity of an ecosystem?

Answer 11

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

Question 12

What are density-independent factors?

Answer 12

Factors which have the same intensity of impact whether the population is sparse or overcrowded.
- Weather, climate change, natural disasters

Question 13

What are density-dependent factors?

Answer 13

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 14

What is natural selection?

Answer 14

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 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 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 needed for evolutionary change to occur?

Answer 20

The traits must be heritable.

Question 21

What is genetic variation?

Answer 21

Different phenotype or differences between individuals in a population / species.

Question 22

What is fitness?

Answer 22

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

Question 23

What is the process of evolution by natural selection?

Answer 23

1. Genetic variation -
2. Intraspecific competition -
3. Survival -
4. Inheritance -

Question 24

What is sexual selection?

Answer 24

The concept that many animals choose with whom they mate.

Question 25

What affects the success in attracting mates?

Answer 25

Differences in physical and behavioural traits and can affect success in attracting a mate and reproducing, and so drive the evolution of an animal population.

Question 26

How does sexual selection acts as a selection pressure in animal species?

Answer 26

Some traits are more preferred by mates as they can be used as signs of overall fitness, indicating their offspring would likely have the traits needed to survive also.
- Therefore sexual selection increases the changes of survival and reproduction of individuals with the favoured traits, meaning those organisms will leave more offspring and pass the allele(s) for the trait to those offspring.
- The alleles become more frequent in the population.

Question 27

What are behavioural trait examples?

Answer 27

An individual will only have enough energy to perform courtship behaviours such as a mating ritual dance (eg, Peacock spiders) or building a structure (eg, Bower birds) if they have gained enough resources to exceed their survival needs.

Question 28

What are physical trait examples using the evolution of the plumage of birds of paradise?

Answer 28

• Male birds of paradise compete for the females, to reproduce.
• The males’ long and brightly coloured plumage attracts a mate (as well as their dance and vocalisations).
• Despite these extreme features making the males more vulnerable to predation, they survive.
• Male birds who are more successful at getting food and keeping safe from predators, will have more available time and energy to maintain extreme colours, healthy plumage (and carry out intricate behaviours).
• Natural selection has benefited the most colourful males with the best reproductive success, thus passing the alleles for this physical trait to their offspring.