Section 7 - Chapter 18: Populations and Evolution - old

Question 1

What is discontinuous data and name examples

Answer 1

• Data falls into distinct categories (no intermediate types)
  
  • Gender, Blood Group

Question 2

What is continuous data and name examples

Answer 2

• Data can have intermediate values - no distinct categories
• Arm span, skin tone, height

Question 3

What are the 2 different types of factors that show variation in phenotype

Answer 3

• Genetic and environmental factors

Question 4

Genetic variation arises as a result of…

Answer 4

• Mutations - changes in DNA base sequence
• Meiosis - creates new combinations of alleles
• Random Fertilisation of gametes

Question 5

Where variation is due to genetic factors organisms fit into …. known as …..

Answer 5

Where variation is due to genetic factors organisms fit into a few distinct categories known as discontinous data

Question 6

What is genetic variation controlled by and how can this be graphically represented

Answer 6

• Controlled by a single gene
• Bar chart or pie chart

Question 7

Name sone environmental factors that can influence how genes are expressed

Answer 7

• Climatic conditions, temperature, rainfall, soli conditions, food availability

Question 8

What is a continuum and how is environmental factors controlled by

Answer 8

• Some characteristics grade into 1 another
• Not controlled by a single gene but by many genes (polygenes)

Question 9

How can environmental variation be graphically presented

Answer 9

Line-graph, bell-shaped curve, normal distribution curve

Question 10

What are the environmental factors that limit the population of species called and name examples

Answer 10

• Selection Pressures - these determine the frequency of alleles within a gene pool
• Predation, competition and disease

Question 11

What is a gene pool

Answer 11

• Is the total number of all the alleles of all the genes of all the individuals within a particular population at a given time

Question 12

What are the factors that the process of evolution by natural selection depends on

Answer 12

• Organisms produce more offspring than can be supported by the available supply of food, light, space
• There is genetic variety within the populations of all species
• A variety of phenotypes that selection operates against

Question 13

What is the link between natural selection and over production

Answer 13

• When there are too many offspring for the available resources, there is competition amongst individuals
• The greater the numbers, greater the competition - more death
• Individuals best suited survive and breed and pass on favourable alleles to offspring

Question 14

What is the role of variation in natural selection

Answer 14

• Conditions change over time and having a wide range of different alleles means some will have combinations needed to survive.
• These survive and pass on favouable alleles - change allele frequency

Question 15

What happens to populations that show little genetic variation

Answer 15

• More vulnerable new diseases and climate change

Question 16

What are the 3 main types of selection that affect characteristics of a population

Answer 16

• Stabilising Selection
• Directional Selection
• Disruptive Selection

Question 17

What is Selection

Answer 17

• A process by which only the organisms better adapted to their environment, survive, breed and pass on favourable alleles

Question 18

What is Stabilising Selection and name an example

Answer 18

• Eliminates the extremes of the phenotype. It favours the mean
• It tends to occur when environmental conditions are constant over a period time
• Reduces range of phenotype
• Human birth weight

Question 19

What is Directional Selection and name an example

Answer 19

• 1 extreme phenotype more likely to survive
• Environment changes characteristics of the population changes over time
• Peppered moths

Question 20

What is Disruptive Selection

Answer 20

• 2 different extremes are favoured
• When an environmental factor such as temperature takes 2 or more distinct forms

Question 21

What is allelic frequency

Answer 21

• The number of times an allele occurs in a gene pool this affected by selection

Question 22

What is speciation

Answer 22

• Is the evolution of new species from existing ones
• Members of a species are reproductively separated from other species
• It is through speciation that evolutionary change has happened over millions of years

Question 23

How are new species formed

Answer 23

• Through reproductive separation followed by genetic change due to natural selection

Question 24

What is adaptive radiation

Answer 24

Different phenotypes each combination of alleles produces due to selection pressures that will lead to the population being adapted and results in changes in the allele frequencies

Question 25

How a new species is formed summary

Answer 25

1. **Population** becomes separated (could be due to **geographical isolation** which causes reproductive isolation/separation) 2. Within a population **genetic variation** exists (due to **mutations**) 3. No **interbreeding** 4. Each new environment exerts different **selection pressures** and **species** become adapted to their own environment **(adaptive radiation)** 5. Best adapted are selected - natural selection 6. Causes change in **allele frequency** 7. If 2 populations come back they can't interbreed - **speciation.** Gene pools are different

Question 26

What is genetic drift

Answer 26

* Takes place in small populations - possess small variety of alleles * This is when chance rather than the environment dictates which organisms survive and breed

Question 27

What are the 2 forms of speciation

Answer 27

* Allopatric * Sympatric

Question 28

What is Allopatric Speciation

Answer 28

* Where 2 populations become geographically separated * These barriers include oceans, rivers, mountains * Physical barriers prevent interbreeding (reproductively isolated) * Environmental conditions can vary either side, then natural selection will influence 2 populations differently and each will evolve leading to changes in allelic frequencies

Question 29

What is sympatric speciation

Answer 29

* Speciation that results within a population in the same area leading them to be reproductively isolated * Not Geographically isolated

Question 30

Why populations maybe reproductively isolated if there is no Barrier

Answer 30

* Mutations * They develop differences in their gene pools e.g. changes in courtship behaviours, seasonal differences * Therefore, different alleles selected for and passed on - changes allele frequency * Example of disruptive natural selection

Question 31

Name some reproductive isolation mechanisms

Answer 31

* Behavioural - produce different songs/ colourings - don't attract mates * Mechanical - change in genitalia - physically not possible * Temporal - Different flowering times

Question 32

How can speciation occur in plants

Answer 32

* A random mutation that causes plants to become polyploidy (extra set of chromosomes) * Those with polyploidy can't breed to produce fertile offspring - therefore reproductively isolated * If species reproduces asexually and survives the mutation, a new species can develop. *

Question 33

Exam Question: The 2 species diverged from each other after the island was formed 6.5 million years ago. The flowering times of the 2 species are different. Suggest how the 2 species arose by sympatric speciation

Answer 33

1. Occurs in the same environment 2. Mutations cause different flowering times 3. Reproductive separation/isolation 4. Different alleles passed on/ change in frequency of alleles 5. Disruptive natural selection 6. Eventually different species can't interbreed to produce fertile offspring 7.

Question 34

What are the factors that affect allele frequencies

Answer 34

* Natural Selection * Mutations * Genetic Drift - when chance rather than the environment dictates which survive - impacts smaller populations

Question 35

What is the founders effect

Answer 35

* The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population

Question 36

What is Genetic Bottlenecks

Answer 36

* A sharp reduction in population sizes due to environmental events and human activities * Population bottlenecks produce a smaller population with reduced genetic diversity * In subsequent generations, genetic diversity remains lower only increase by mutations.