Topic 6 - Inheritance, Variation and Evolution (2)

Question 1

REPRODUCTION:
What does sexual reproduction produce?

Answer 1

genetically different offspring

Question 2

REPRODUCTION:
What happens in sexual reproduction?

Answer 2

• genetic information from 2 organisms (father and mother) are combined to produce offspring that are genetically different to either parent
• the mother and father produce gametes by meiosis e.g. egg and sperm cells in animala

Question 3

REPRODUCTION:
What is the process in which the mother and father prosuce gametes?

Answer 3

meiosis

Question 4

REPRODUCTION:
In humans, how many chromosomes does each gamete contain?
Compare this to normal cells

Answer 4

23 - half the number of chromosomes in a normal cell
- instead of having two of each chromosome, a gamete just has one of each

Question 5

REPRODUCTION:
What is the name of the process where the egg and sperm fuse together?

Answer 5

fertilisation

Question 6

REPRODUCTION:
What happens in fertilisation?

Answer 6

the egg (from the mother) and the sperm cell (from the father) fuse together
this forms a cell with the full number of chromosomes - half from the mother and half from the father
(as each gamete only has 23 chromosomes)

Question 7

REPRODUCTION:
What are the main characteristics of sexual reproduction?

Answer 7

• involves the fusion of male and female gametes
• there are 2 parents
• so the offspring contain a mixture of their parent’s genes

Question 8

REPRODUCTION:
Why do offspring from sexual reproduction inherit characteristics from both parents?

Answer 8

• its recieved a mixture of chromosomes from its mum and dad
• its the chromosomes that determine the characteristic you have

Question 9

REPRODUCTION:
In sexual reproduction, what does the mixture of genetic information produce?

Answer 9

variation in the offspring

Question 10

REPRODUCTION:
When flowering plants reproduce sexually, what are their gametes?

Answer 10

• egg cells (female)
• pollen (male)

Question 11

REPRODUCTION:
What does asexual reproduction produce?

Answer 11

genetically identical offspring

Question 12

REPRODUCTION:
What type of reproduction only involves one parent and what does this mean for the offspring?

Answer 12

• asexual reproduction
• the offspring are genetically identical to their one parent

Question 13

REPRODUCTION:
What process happens in asexual reproducton?

Answer 13

• asexual production only involves mitosis (an ordinary cell makes a new cell by dividing in 2)

Question 14

REPRODUCTION:
Asexual reproduction: when the new cell had exactly the same genetic information (genes) as the parent cell, what is it called?

Answer 14

a clone

Question 15

REPRODUCTION:
What are the main characteristics of asexual reproduction?

Answer 15

• only one parent
• no fusion of gametes
• no mixing of chromosomes
• no genetic variation between parent and offspring
• the offsping are genetically identical to the parent (they are clones)

Question 16

REPRODUCTION:
What types of organisms reproduce asexually?

Answer 16

• bacteria
• some plants
• some animals

Question 17

MEIOSIS:
What does meiosis produce?

Answer 17

gametes

Question 18

MEIOSIS:
Why do gametes only contain one copy of each chromosome?

Answer 18

so that when gamete fusion takes place, the zygote has the right amount of chromosomes (two copies of each)

Question 19

MEIOSIS:
How are gametes made to only have half the number of original chromosomes?

Answer 19

cells divide by meiosis

Question 20

MEIOSIS:
How many cell divisions does meiosis involve?

Answer 20

2

Question 21

MEIOSIS:
Where does meiosis happen in humans?

Answer 21

it only happens in the reproductive organs (ovaries in females and the testes in males)

Question 22

MEIOSIS:
What happens after two gametes have fused during fertilisation?

Answer 22

• the resulting new cell divides by mitosis to make a copy of itself
• mitosis repeates many times to produce lots of new cells in an embryo
• these cells then start to differentiate into different types of specialised cell that make up a whole organism

Question 23

REPRODUCTION:
What type of reproduction causes variation in the offspring and how?

Answer 23

Offspring from sexual reproduction hane a mixture of two sets of chromosomes
The organsim inherits genes from both parentsm which produces variation in the offspring

Question 24

REPRODUCTION:
How can varition be useful to a species?

Answer 24

it increases the chance of species being able to survive a change in the environment
Whilst the change may kill some induviduals, it’s likely that variation will have led to some of the offspring being able to survive in the new environment - they have a survival advantage

Question 25

REPRODUCTION: What happens to organisms better adapted to the changing environment? What is this known as?

Answer 25

induviduals with characteristics that make them better adapten to the environment have a better chance of survival, they are more likely to breed successfully and pass on the genes for the characteristics - this is known as NATURAL SELECTION

Question 26

REPRODUCTION: What is selective breeding and how does it allow us to speed up the process of natural selection? Why woul we want to do this?

Answer 26

- Selective breeding is where induviduals with a desirable characteristc are bred to produce offspring with a desirable characteristic too - this allows us to produce offspring with desirable characteristics, meaning we can increase food production e.g. by breeding animals that produce a lot of meat

Question 27

REPRODUCTION: What are the advantages of asexual reproduction?

Answer 27

1) there only needs to be one parent 2) this means it uses less energy than sexual reproduction as organisms don't need to find a mate 3) it is also faster than sexual reproduction 4) many identical offspring can be produced in favourable conditions

Question 28

REPRODUCTION: REMEMBER: Some organisms can produce sexually or asexually depending on their circumstances

Question 29

REPRODUCTION: Name a communicable disease causing parasite that can reproduce both sexually and asexually? When does it do this?

Answer 29

Malaria (caused by a parasite spread by mosquitos) - when a mosquito carrying the parasite bites a human, the parasite can be transferred from the human - the parasite produces sexually when it's in the mosquito and and asexually when it is in the human host

Question 30

REPRODUCTION: Name 3 different organisms that can reproduce sexually and asexually?

Answer 30

1) the parasite that causes malaria 2) many species of fungus 3) many plant species

Question 31

REPRODUCTION: Why do some species of fungus produce both sexually and asexually?

Answer 31

these species produce spores, which can become new fungi when they land in asuitable place - they can be produced sexually and asexually - asexually produced spores form fungi that are genetically identical to the parent fungus - sexually produced spores introduce variation often i preduced in response to an unfavorable change in the environment, increasing the chance that the population will survive the change

Question 32

REPRODUCTION: Give two examples of where asexual reproduction may appen on different plant species?

Answer 32

- runners on strawberry plants - plants that grow from bulbs

Question 33

REPRODUCTION: Explain where asexual reproduction would happen on a strawberry plant?

Answer 33

strawberry plants produce 'runners' - these are stems that grow horizontally on the surface of the soil away from the plant. At various points along the runner, a new strawberry plant forms that is identical to the original plant

Question 34

REPRODUCTION: Explain how asexual reproduction may happen in plants that grow from bulbs?

Answer 34

in plants like daffodils, new bulbs can form from the main bulb and divide off, each bulb can grow into a new identical plant

Question 35

X and Y chromosmes: How many pairs of chromosomes are there in every human cell? How many of these pairs control characteristics or your sex?

Answer 35

23 - 22 are matched pairs of chromosmes that just control characteristics - the 23rd pair are the two chromosmes that decide your sex

Question 36

X and Y chromosmes: Which different chromosomes combination allow for male or female characteristics?

Answer 36

Males have an X and Y chromosome: XY - the Y chromosome causes male characteristics Females have 2 X chromosomes: XX - the XX combination allows female characteristics to develop

Question 37

X and Y chromosmes: Which X or Y chromosomes does each gamete have and how do they develop this?

Answer 37

- When making sperm, the X and Y chromosomes are drawn apart in the first division of meiosis. There's a 50% chance each sperm cell gets an X chromosome or a Y chromosome - A similar thing happens when making eggs. But as the original cell has 2 X chromosomes all the eggs have 1 X chromosome

Question 38

X and Y chromosmes: What can you use to find the probability of getting a boy or girl?

Answer 38

a genetic diagram

Question 39

X and Y chromosmes: What are genetic diagrams?

Answer 39

models used to show all the possible genetic outcomes when you cross together different genes or chromosomes