Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Year 8 Science > 8J Genes > Flashcards

8J Genes Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Identify two resources that organisms compete for.

A

Food, water, space, mates, light (plants only)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define variation

A

Difference between individuals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is evolution?

A

A gradual change over time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why do organisms produce more offspring that is needed?

A

To increase the chance that some of them will survive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do we mean by the “fittest” organism will survive?

A

The best adapted organism will survive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What animal did Darwin study when developing the theory of natural selection?

A

Galapagos finches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What was different about these animals?

A

Beak shape and size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why were their differences important to Darwin’s theory?

A

Different beaks were better adapted to eat the different food available on different islands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Define biodiversity

A

The variety of living things within an ecosystem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

State two ways we measure biodiversity

A

Number of different species, differences between individuals of same species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why do humans rely on plants?

A

Plants take in CO2 and produce O2, for food for us and the animals we eat, for medicines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why is a reduction in biodiversity bad for humans?

A

Less likely that we had all of the resources that we depend upon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is interdependence?

A

All organisms in a habitat rely on each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why are food chains more stable in high biodiversity ecosystems?

A

Removal of one species is less likely to have a massive impact on the rest of the food web.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What do we mean by the term “endangered species”?

A

When there are few individuals left of a species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Define extinct

A

When a species has died out and there are no more left

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a mass extinction?

A

The extinction of many species all at once

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When was the last mass extinction?

A

65 million years ago

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

State two natural causes of extinction.

A

Climatic heating and cooling, changes in sea level, asteroid impacts, disease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

State two ways that human activities cause extinction.

A

Hunting, habitat destruction, introduction of invasive species, over-exploitation of wildlife

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a gene bank?

A

A collection of seeds, sperm, eggs, embryos, blood and cuttings to preserve the genetic material of endangered plants of animals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why is the Northern white rhino described as extinct, even though there are two individuals still alive?

A

Both are females so cannot reproduce

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What did scientists use to create a cloned Pyrenean ibex?

A

A frozen sample of tissue and a Spanish Ibex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

In which part of the cell is an organism’s genetic material found?

A

Nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What does DNA stand for?

A

Deoxyribonucleic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How many pairs of chromosomes do humans have?

A

23 pairs (46 chromosomes in total)

27
Q

What is a gene?

A

Short sections of DNA that code for proteins

28
Q

What shape is DNA?

A

Double helix

29
Q

What are the base pairs?

A

A and T, C and G

30
Q

Why is detergent added to the ground up fruit?

A

To break down the cell and nucleus membrane, to release the DNA

31
Q

What is used to separate DNA from a solution?

A

Ethanol – DNA is insoluble in ethanol so will form a separate layer

32
Q

Name the four scientists who discovered the structure of DNA.

A

Watson, Crick, Franklin, Wilkins

33
Q

When was the structure of DNA discovered?

A

1950s

34
Q

How was X-ray crystallography used to discover the structure of DNA?

A

It was used to photograph the double helix shape of DNA

35
Q

What did Erwin Chargaff contribute to the discovery of the structure of DNA?

A

Found out that DNA was made of base pairs – A, T, C and G

36
Q

How was the final model of DNA created?

A

Franklin’s x-ray photograph and Chargaff’s base pairs were used to build a model

37
Q

Why were only three scientists awarded a Nobel Prize for their discovery?

A

Franklin died before the prize was awarded

38
Q

Why did these four scientists have to collaborate to discover the structure of DNA?

A

They each contributed something different to the discovery

39
Q

What is the Human Genome Project?

A

A project to discover the exact sequence of base pairs in every gene in every chromosome in a human cell

40
Q

What is a gamete?

A

Sex cell, e.g. a sperm or egg

41
Q

Why do gametes have half a set of chromosomes?

A

So that when they join they have a full set

42
Q

How is a karyotype prepared?

A

Chromosomes are separated from the cell and spread out on a microscope slide

43
Q

Why is there variation amongst the offspring of two parents?

A

The alleles in each sperm or egg are completely random

44
Q

What is trisomy?

A

When three chromosomes are inherited instead of a pair

45
Q

What are the effects of trisomy 21?

A

Down’s syndrome

46
Q

Give an example of a genetic disorder not caused by trisomy.

A

Sickle cell anaemia, cystic fibrosis

47
Q

What is a carrier?

A

Someone who carries the allele for a disease but does not have the disease itself. They can pass it on to their children

48
Q

What is an inherited characteristic?

A

Characteristics that are inherited from parents through the genes

49
Q

Give an example of a human inherited characteristic.

A

Eye colour, blood type, freckles

50
Q

How many chromosomes does each parent pass on to their offspring?

A

Half a full set, e.g. 23 for humans

51
Q

Why do siblings look similar, but not identical?

A

They share some characteristics from each parent

52
Q

What happens to produce identical twins?

A

A fertilised egg splits to produce two foetuses

53
Q

Define what an embryo is.

A

An early stage of development of an animal, a small ball of cells

54
Q

Why are identical twins never exactly the same?

A

Environmental factors affect their appearance

55
Q

How are non-identical twins produced?

A

Two eggs, released at the same time, are fertilised by separate sperm

56
Q

Why do we use models of inheritance?

A

To predict the likelihood of inheriting certain genes

57
Q

What is an allele?

A

Different forms of the same gene

58
Q

Why is the brown fur allele described as dominant?

A

It is always expressed even if there is only one copy of the brown allele

59
Q

Why is the white fur allele described as recessive?

A

It is only expressed if both alleles are for white fur

60
Q

Why is it not possible to know the alleles of a brown mouse?

A

It may have two brown alleles, or one brown and one white allele

61
Q

How many possible combinations of alleles are there?

A

Three

62
Q

For the Punnett square above, what are the chances the mouse will be brown?

A

¾ or 75%

63
Q

Why is it more likely that a mouse will be brown than white?

A

Brown is the dominant allele, only one needs to be inherited to be expressed

Year 8 Science (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions