D4.1

Question 1

what is natural selection

Answer 1

It all starts with the (D4.1.3) overproduction of offspring and

the presence of (D4.1.2) natural variation in the population;

Then there is a (D4.1.3 and D4.1.4) struggle between competing varieties

That leads to (D4.1.5) survival for some and

Be able (D4.1.6) pass the genes to the next generation

And death for others

Question 2

what does mutation do

Answer 2

Mutation generates new alleles and sexual reproduction generates new combinations

Question 3

Sources of variation

Answer 3

Mutations in DNA
Meiosis
Sexual reproduction

Question 4

Variation: Mutations in DNA

Answer 4

Some mutations can lead to genetic diseases which could kill an individual

Other mutations can be beneficial (e.g. enhanced ability or some features which allows the individual to survive better)

However, most of the time, mutations produce effects that are neither useful nor harmful (cannot rely on mutation alone to improve the chance of survival)

Question 5

Variation: Meiosis

Answer 5

Meiosis is a kind of cell division in which (reproductive cells) male and female gametes are made

• sperms and ova (singular: ovum) in animals
• male gametes in pollen grains and female gametes in ovules in flowering plants

THey only have half the amount of chromosomes (DNA) comparing to the somatic cells (any cell of a living organism other than gamete)

Variation of gametes arise mainly from the process of random orientation during metaphase 1. The lining up of chromosomes is random. crossing over helps shuffle genetic material and increases genetic variety further

Question 6

Variation: Sexual reproduction

Answer 6

Possessing some characteristics may favour an individual which may affect survival and opportunities to reproduce

Question 7

Examples of variation of sexual reproduction

Answer 7

Birds with more colourful feathers to attract mates

Animals with stronger leg muscles to run away from predators

Organisms with enzymes that can stay active for a larger range of temperature/pH

Question 8

what is asexual reproduction

Answer 8

Asexual reproduction produces genetically identical offspring/second generation

Question 9

what is overproduction

Answer 9

Many of the living organisms produce a lot of offspring (but the number of individuals in species remains more or less constant, so there must be a high mortality rate

It requires a large amount of energy and nutrients to produce a large amount of seeds, spores or eggs (this can affect the survival rate of the parents especially when the resources are limited)

This is to maximise the chances of some offspring surviving

Question 10

carrying capacity

Answer 10

Carrying capacity refers to the maximum number of organisms that an environment can provide for, resources like food, water, space, sunlight will determine the carrying capacity of an environment

Question 11

what is selection pressure

Answer 11

Selection pressures are external agents which affect an organism’s ability to survive in a given environment

Question 12

density dependent factors

Answer 12

PANDA

Predators
Availability of resources (shelter, water)
Nutrient supply (i.e. food source)
Disease / pathogenic spread
Accumulation of wastes

Question 13

density independent factors

Answer 13

PAW

Phenomena (e.g. natural disasters)
Abiotic factors (e.g. temperature, CO2 levels)
Weather conditions (e.g. floods, storms, etc.)

Question 14

what is intraspecific competition

Answer 14

Competition between individuals from the same species

Compete for the same type of resource

Question 15

Example of adaptations for intraspecific competition

Answer 15

plover egg and chicks

effective camouflage protect them from eaten by predator (if some mutations cause the shell or the chicks to become attractive to predators, then those mutated genes would not be able to pass to the next generation)

Question 16

Heritable traits

Answer 16

Heritable traits refers to features or characteristics that are driven by the organism’s DNA (not due to acquired skills or ability), these traits can be passed down to the next generation

Question 17

acquired traits

Answer 17

Acquired characteristics refers to some features that the organisms acquired through its lifetime, these characteristics cannot be passed down to the offspring

Question 18

Sexual selection

Answer 18

Male compete for access to females, who being present to mate with females, and even whose sperm gets to fertilise her eggs. For example, male damselflies scrub sperm out of the female reproductive tract when mating

Question 19

sexual dimorphism

Answer 19

Sexes of the same species display different morphological characteristics

Male birds with colourful and shiny features as an indication of the health of the male

Female birds with cryptic coloration for camouflage and able to hide from predators

Question 20

Female choice

Answer 20

Females choose which males to mate with, how long to mate, and even whose sperm will fertilise her eggs. Some females can eject sperm from an undesirable mate.

Question 21

what is gene pool

Answer 21

A gene pool consists of all the genes and their different alleles, present in a population

Question 22

inbreeding

Answer 22

Refers to the mating of close relatives in species
Reduces the genetic diversity

Question 23

Allele frequency

Answer 23

it is the measure of the proportion of a specific version of a gene in a population

Question 24

Alleles and evolution

Answer 24

Immigration and emigration may change the allele frequency of a population

Mutations may introduce new alleles to a population

Some alleles may disappear in a population if the individuals carrying those alleles die

Some alleles that are not advantageous to the survival of organisms in a population (e.g. disease causing) may have different effects on the population depending on the nature of the alleles (dominant vs recessive traits)

Question 25

stabilising selection

Answer 25

Where an intermediate phenotype is favoured at the expense of both phenotypic extremes

This results in the removal of extreme phenotypes (phenotypic distribution becomes centrally clustered to reflect homogeneity)

Question 26

stabilising selection example

Answer 26

Human birth weight
Babies of low weight lose heat more quickly and get ill from infectious diseases more easily. Babies of large body weight are more difficult to deliver through the pelvis. Medium weight babies have a much lower mortality and hence the frequency of medium weight babies increases

Question 27

directional selection

Answer 27

Where one phenotypic extreme is selected at the cost of the other phenotypic extreme

This causes the phenotypic distribution to clearly shift in one direction (towards the beneficial extreme)

Question 28

directional selection example

Answer 28

Darwin finches

Years of drought caused the medium ground finches living on Daphne Major to shift the beak size from a normal distribution to mostly having larger beaks to help the finches to crush larger and drier seeds produced by drought tolerant plants.

Question 29

disruptive selection

Answer 29

Where both phenotypic extremes are favoured at the expense of the intermediate phenotypic ranges

This causes the phenotypic distribution to deviate from the centre and results in a bimodal spread

Question 30

disruptive selection examples

Answer 30

Different morphologies of the tadpoles of spadefoot toads

One is an omnivorous diet and one is strictly carnivorous diet. Less overlapping of diet choices within the same population and reduce intraspecific competition

Question 31

Natural selection and antibiotic resistance

Answer 31

Example of natural selection is antibiotic resistance in bacteria

Antibiotics like penicillin can kill/inhibit the growth of bacteria

Explain why doctors ask patients to complete the full course of antibiotics, even if they start to feel better

Explain why the medical profession tries to combat resistance by alternating the types of antibiotics used against an infection