B4 - Natural Selection and Genetic Modification

Question 1

Define

evolution.

Answer 1

the slow and continuous change of organisms from one generation to the next

Question 2

Describe the process of

natural selection.

(6 steps)

Answer 2

1. Individuals in a population have genetic variation due to difference in their alleles.
2. Competition for resources, predation and disease affect an organism’s chance of surviving and reproducing.
3. Those individuals with characteristics that make them better adapted to their environment have a better chance of survival, so are more likely to breed successfully.
4. The alleles that are responsible for the useful characteristics are more likely to be passed on to the next generation.
5. Some individuals will be less well adapted to the environment and will be less able to compete. So, are less likely to survive and reproduce.
6. The beneficial characteristics become more common in the population over time.

Question 3

Define

fossil.

Answer 3

a trace of an animal or plant that lived a long time ago

(over a thousand years ago)

Question 4

What are two

evidences for evolution?

(2)

Answer 4

• antibiotic resistance of bacteria
• fossils

Question 5

What did

Charles Darwin do?

(4 steps)

Answer 5

1. Spent 5 years on a voyage around the world studying plants and animals on a ship called the HMS Beagle.
2. Noticed that there was variation in members of the same species and that those with characteristics most suited to the environment were more likely to survive.
3. Noticed that the characteristics could be passed on to offspring.
4. Wrote the book ‘On the Origin of Species’ explaining his observations

Question 6

What did

Alfred Wallace do?

(2 things)

Answer 6

1. Came up with the idea of natural selection independently of Darwin.
2. Observed lots that helped evidence the theory of evolution by natural selection.

Question 7

In what areas have

ideas about evolution influenced modern biology?

(3)

Answer 7

• classification - organisms are classified by how closely related they are
• antibiotic resistance - the course of drugs must be finished to prevent resistant bacteria spreading, new antibiotics must be constantly developed to fight newly evolved resistant bacteria
• conservation - gentic diversity is very important as it helps populations adapt to changing environments

Question 8

What are

hominids?

Answer 8

human beings and their ancestors

Question 9

Tell me about

Ardi.

• full name?
• age?
• location?

Answer 9

• Ardipithecus ramidus
• 4.4 million years old
• Ethiopia

Question 10

What are some

characteristics of Ardi?

(4)

Answer 10

1. Feet structured to climb trees - ape-like big toe.
2. Long arms, short legs
3. Small brain size
4. Walked upright - deduced by leg structure and hand bone structure

Question 11

Tell me about

Lucy.

• full name?
• age?
• location?

Answer 11

• Australopithecus afarensis
• 3.2 million years old
• Ethiopia

Question 12

What are some characteristics of

Lucy?

(4)

Answer 12

1. Arched feet and no ape-like big toe - more adapted to walking than climbing.
2. Shorter arms and legs (than Ardi).
3. Slightly larger brain (than Ardi).
4. Walked upright, more efficiently (than Ardi) - deduced by leg and feet bone structure.

Question 13

Tell me about

Turkana boy.

• discovered by?
• location?
• age?
• species name?

Answer 13

• discovered by Richard Leakey
• Kenya
• 1.6 million years old
• Homo erectus

Question 14

What are some characteristics of

Turkana boy?

(4)

Answer 14

• has a mixture of human and ape-like features (more human-like than Lucy)
• has short arms and long legs
• much larger brain size (than Lucy)
• even better adapted to walking upright (than Lucy)

Question 15

What are some ways in which

scientists can work out how old a fossil or stone tool is?

(3)

Answer 15

1. Look at the structual features of the tool or fossil.
2. Study the rock layers.
3. Use carbon-14 dating to date materials used in stone tools.

Question 16

What is a

pentadactyl limb?

Answer 16

a limb with five digits

Question 17

How does the

pentadactyl provide evidence for evolution?

Answer 17

the similarity in bone structure of pentadactyle limbs provides evidence that the species have all evolved form a common ancestor (that had a pentadactyl limb)

if they’d all evolved from different ancestors, then it’d be highly unlikely that they’d share a similar bone structure

Question 18

How were organisms classified in the

five kingdom classification system?

Answer 18

according to similarities and differences in organisms observable characteristics

Question 19

What are the

five kingdoms?

(of the five kingdom classification system) (+ examples)

Answer 19

• Animals - fish, mammals, reptiles
• Plants - grass, trees
• Fungi - mushrooms, yeast
• Prokaryotes - single-celled organisms without a nucleus
• Protists - eukaryotic single-celled organisms, algae

Question 20

Why have

classification systems changed over time?

Answer 20

Over time, technology has developed further and our understanding of things like biochemical processes and genetics has increased.
Organisms are now classified using RNA sequencing.

Question 21

What are the

three domains?

(of the three domain classification system)

Answer 21

• Archaea
• Bacteria
• Eukarya - e.g. fungi, animals, plants, protists

Question 22

Define

selective breeding.

Answer 22

the process of humans artificially selecting the plants or animals that are going to breed so that genes for particular characteristics remain in the population

Question 23

What are some examples of

selectively bred organisms?

(4)

Answer 23

• animals that produce more meat or milk
• crops with disease resistance
• dogs with good, gentle temperament
• plants that produce bigger fruit

Question 24

How has selective breeding been used in

medical research?

Answer 24

When investigating alcoholism, rats have been bred with either a strong or weak preference for alcohol. This has allowed researchers to compare the differences between the two different types of rats.

This includes differences in their behaviour and in the way that their brains work.

Question 25

# What is the main disadvantage of selective breeding? | and why is this so bad?

Answer 25

**Inbreeding** - selective breeding **reduces** the **gene pool**, resulting in **closely related** animals or plants being bred. This can cause **health problems** because there's more chance of organisms inheriting **harmful genetic defects**. ## Footnote This can also be a serious problem if a **new disease** appears. There's not much **variation** in the population, so there's **less chance** of **resistant alleles** being present. So, if one stock is killed by a **new disease**, the others are **also** likely to succumb to it.

Question 26

# What does tissue culture involve?

Answer 26

growing cells on an **artifical growth medium**

Question 27

# What are the advantages of tissue culture? | (5)

Answer 27

- easy - very quick - takes little space - can be grown all year - can create clones with the same beneficial features

Question 28

# Describe the process of tissue culture. | (of plants) (4 steps)

Answer 28

1. Choose the plant you wish to clone based on its **characteristics**. 2. **Remove** several **small pieces** of **tissue** from the **parent plant**. 3. Grow the tissue in a **growth medium** containg **nutrients** and **growth hormones**. 4. As the tissues produce roots and shoots they can be moved to **potting compost** to carry on growing.

Question 29

# Why should tissue culture be made in aseptic conditions?

Answer 29

in order to prevent the growth of **microbes** that could harm the plants

Question 30

# Why is animal tissue culture often used in medical research?

Answer 30

**Experiments** can be carried out on tissues in **isolation** in order to look at the effects of a **particular substance** or **environmental change** on the cells of a **single tissue**, without complications from other processes in the **whole** organism.

Question 31

# Describe the process of tissue culture of animal cells. | (4 steps)

Answer 31

1. **Extract** a **sample** of the **tissue** you want to study from the animal. 2. **Separate** each of the cells using **enzymes**. 3. Place the cells in a **culture vessel** and bathe them in a **growth medium** containing all the **nutrients** necessary. 4. After several round of **cell division**, **split** the cells **up** again and place them into **separate vessels** to encourage further growth. | Once the tissue culture has been grown, it can be stored for future use.

Question 32

# What does genetic engineering involve?

Answer 32

modifying an organism's **genome** to introduce **desirable characteristics**

Question 33

# Define recombinant DNA.

Answer 33

**two different** bits of DNA that have been stuck together

Question 34

# What do restriction enzymes do?

Answer 34

recognise **specific sequences** of DNA and **cut the DNA** at these points | the pieces of DNA are left with **sticky ends** where they have been cut

Question 35

# What does ligase (enzyme) do?

Answer 35

join **two pieces of DNA** together at their **sticky ends**

Question 36

# What is a vector?

Answer 36

something that is used to transfer DNA into a cell

Question 37

# What are the two types of vector?

Answer 37

- plasmids - viruses

Question 38

# Describe the process of genetic engineering. | (6 steps)

Answer 38

1. Cut out the **DNA** you want to **insert** using a **restriction enzyme**. 2. Cut the **vector DNA** using the **same** restriction enzyme. 3. Mix the vector DNA and insert DNA with **ligase enzymes**. 4. The ligases **join** the pieces of DNA together to make **recombinant DNA**. 5. This DNA is **inserted** into other cells. 6. These cells can now **use the gene you inserted** to **make the protein** you want.

Question 39

# What are some uses of genetic engineering? | (3 things)

Answer 39

- **crops** can be modified to be **resistant to herbicides** - **human genes** that produce **useful proteins** can be transferred to **sheep** and **cows** - so that the proteins can then be **extracted** from the animal - human **insulin** producing **bacteria**

Question 40

# What are some concerns surrounding genetic engineering and its products? | (3)

Answer 40

- it can be hard to predict what **effect** modifying an animal's genome will have **on the organism** - **transplanted genes** (in plants) may get out into the **environment** - genetically modified crops could **adversely** affect **food chains** or even **human health**

Question 41

# Describe how insect resistant plants can be made. | (2)

Answer 41

1. ***Bacillus thuringiensis*** produces a **toxin** that kills many of the **insect larvae** that are harmful to crops. 2. The **gene** for Bt is then inserted into **crops** which then produce the toxin from their **stems** and **leaves** - making them resistant to the insect pests.

Question 42

# Define food security.

Answer 42

the global access to **enough food** that is safe to eat and has the **right balance of nutrition**

Question 43

# What are some concerns surrounding genetically modified crops being used to provide more food for people? | (3)

Answer 43

- many people go hungry because they **cannot afford** to buy food, rather than the lack of food - countries may become **dependent** on **companies** who **sell** GM seeds - sometimes it is **poor soil** that is the main reason why **crops fail**, so even GM crops **won't survive**