Variation And Evolution

Question 1

What is variation

Answer 1

All the differences in the characteristics of individuals in a population

Question 2

Causes of variation

Answer 2

Genetic variation from alleles eg: eye color
Environment eg: language
Genes and the environment eg: height

Question 3

What are mutations affect on the phenotype

Answer 3

Most mutations have no affect on the phenotype
Some mutations can influence the phenotype
A small number of mutations influence the phenotype

Question 4

Explain how a mutation can lead to a new phenotype

Answer 4

Sometimes the new phenotype can be beneficial if the environment changes
This can lead to a rapid change in the species

Question 5

What is evolution

Answer 5

A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

Question 6

What is natural selection

Answer 6

A process where organisms that are better adapted to an environment will survive and reproduce passing on the advantageous alleles to the offspring

Question 7

How is a new species formed from one species

Answer 7

If two populations of one species become so different in phenotype they can no longer interbreed to produce fertile offspring they have formed two new species

Question 8

What is selective breeding

Answer 8

The process by which humans breed plants and animals for particular genetic characteristics

Question 9

Examples of selective breeding

Answer 9

Domestic dogs have been selectively bred to have a gentle nature
Food crops such as wheat have been selectively bred to be resistant to disease
Animals such as cows have been selectively bred to produce more meat or milk
Certain plants have been selectively bred to produce large or unusual flowers

Question 10

Describe how selective breeding is carried out

Answer 10

Take a mixed population of the animal and select the male and female with the desired characteristics
Then breed these together
From the offspring those with desired characteristics are bred together
This continues over many generations until all the offspring show the desired characteristic

Question 11

What’s a problem with selective breeding

Answer 11

If we breed together closely related animals or plants then we can get inbreeding
Inbreeding can cause some breeds to be prone to disease or inherited defects

Question 12

What is genetic engineering

Answer 12

Genes from one organism are cut out and transferred to a cell of a different organism
The genome of an organism is now modified by introducing a gene from another organism to give a desired characteristic

Question 13

Explain how bacteria have been genetically modified

Answer 13

Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes

Question 14

Explain how plant crops have been genetically engineered

Answer 14

They have been genetically engineered to be resistant to diseases or to produce bigger better fruits
GM crops are resistant to insect attacks and generally show increased yields
However, some people question If they are harmful and feel we need to do more research on the health effects of eating GM crops

Question 15

What is gene therapy

Answer 15

Genetic modification is being explored as a way to treat inherited disorders in humans

Question 16

What are the steps of genetic engineering

Answer 16

Identify the gene we want to transfer
Then use enzymes to isolate the gene
Transfer the gene into a plasmid (called a vector)
Instead of using a plasmid you can also use a virus
The desired gene is transferred into the cells of the target organism

Question 17

Why do we always transfer the gene at an early stage in the organisms development

Answer 17

So that the organism develops with the desired characteristic we want

Question 18

Advantages of cloning plants

Answer 18

clone genetically identical to original plant so we know exactly what the characteristics will be

Question 19

Explain how cuttings are used to clone a plant

Answer 19

A small piece of the plant is removed and the end is dipped in rooting powder
Rooting powder contains plant hormones to encourage the plant to develop roots
By taking cuttings we produce a genetically identical clone of the starter plant

Question 20

Explain how tissue culture is used to clone plants

Answer 20

Take a plant that we want to clone and divide it into hundreds of tiny pieces
These small groups of cells are incubated with plant hormones
The hormones stimulate the plant to grow and develop into fully-grown clones

Question 21

Benefits of tissue culture

Answer 21

Extremely useful in commercial plant nurseries
Used to preserve rare species of plants
It allows growers to produce clones of the plant quickly and cheaply
Gardeners can be certain they will get the characteristics they want as they are genetically identical

Question 22

Explain the stages of embryo transplants

Answer 22

Start with sperm and an egg cell from a mammal with characteristics that we want
Fertilisation produces a fertilised egg
Then allow the fertilised egg to develop into an early stage embryo
Use a glass rod to split the embryo into two
Transplant the two embryos into the host mothers
The embryos will then grow and develop
This will produce two identical offspring

Question 23

Problems with embryo transplant

Answer 23

Because we start with a sperm and an egg we cannot be certain that the offspring will have the characteristics we want

Question 24

Describe adult cell cloning

Answer 24

The nucleus is removed from an unfertilised egg cell
The nucleus from an adult body cell such as a skin cell is inserted into the egg cell
An electric shock stimulates the egg cell to divide to form an embryo
These embryo cells contain the same genetic information as the adult skin cell
When the embryo has developed into a ball of cells, it’s inserted into the womb of an adult female to continue its development

Question 25

Benefit of adult cell cloning

Answer 25

Because we are cloning from an adult we know the characteristics that the clone will have

Question 26

What is Darwin’s theory of evolution by natural selection

Answer 26

-Within a species, we can see a wide range of genetic variation for any characteristic
-Individuals with characteristics most suited to the environment are more likely to survive to breed successfully
-The characteristics that have enabled these individuals to survive are then passed on to the next generation

Question 27

Why was Darwin’s theory of evolution by natural selection only gradually accepted

Answer 27

The theory challenged the idea that god made all animals and plants that live on earth.
There was insufficient evidence at the time the theory was published to convince many scientists.
The mechanism of inheritance and variation was not known until 50 years after the theory was published.

Question 28

What is Lamarck’s theory

Answer 28

He suggested that when a characteristic is regularly used, it becomes more developed
This strengthened characteristic is then passed on to the offspring

Question 29

Why is Lamarcks theory incorrect

Answer 29

We now know that in the vast majority of cases, changes that occur in an organisms lifetime cannot be passed onto offspring

Question 30

Describe how Alfred Russel Wallace contributed to our understanding of evolution

Answer 30

Wallace independently proposed the theory of evolution by natural selection
He published joint writings with Darwin in 1858 which prompted Darwin to publish On the Origin of Species
Wallace is best known for his work on warning colouration in animals and his theory of speciation

Question 31

What is speciation

Answer 31

How new species form

Question 32

Describe how new species form

Answer 32

New species arise by isolation:
A population of a species is separated into two due to a geographical barrier
Isolation can prevent interbreeding within a species
Different mutations can take place in the isolated group and create different phenotypes

Question 33

Describe what Gregor Mendel discovered

Answer 33

In the mid 19th century Mendel carried out breeding experiments on plants.
Mendel found that characteristics are not blended during inheritance
Mendel said that characteristics are determined by inherited units and these units do not change when passed on to descendants
These units are now called genes
Mendel also showed that some characteristics could be masked then reappear in later generations
We now call these recessive alleles

Question 34

Explain why the importance of Mendel’s discovery was not recognized until after his death

Answer 34

At the time scientists still believed that characteristics were blended when they are inherited
Soon Mendels work was forgotten
In the late 1800’s scientists looked at how chromosome behave during cell division
They realised Mendel’s units behaved in a similar way to chromosomes
By this time Mendel’s units had been renamed genes
In the mid 1900s scientists determined the structure of DNA and how genes function

Question 35

What are fossils

Answer 35

The remains of organisms from millions of years ago which are found in rocks

Question 36

What are the 3 ways fossils can form

Answer 36

When parts of organisms have not decayed, this happens when the conditions needed for decay are absent.

If parts of the organism are slowly replaced by minerals during the decay process.

Fossils can be the preserved traces of organisms

Question 37

Problem with fossils

Answer 37

Soft-bodied organisms very rarely form fossils or have been destroyed by changes to rocks in the earths crust
Because of this scientists cannot be certain how life on earth began

Question 38

What is extinction

Answer 38

Extinction occurs when there are no remaining individuals of a species still alive

Question 39

What are factors that may contribute to the extinction of species

Answer 39

Due to a catastrophic event
When the environment changes
A new disease or new predator could kill a species
If a new, more successful species evolves and competes with it

Question 40

Why are some bacteria antibiotic-resistant

Answer 40

Mutations of bacterial pathogens produce new strains
New strains of bacteria may be antibiotic resistant
They survive and reproduce so the population of the resistant strain rises
The resistant strain will then spread because people are not immune to it and there is no effective treatment

Question 41

What is an example of an antibiotic resistance bacteria

Answer 41

MRSA

Question 42

What are the ways to reduce the development of antibiotic resistant bacteria

Answer 42

Doctors should not prescribe antibiotics inappropriately
Patients should make sure to complete their course of antibiotics so that all bacteria are killed and none survive to mutate into resistant strains
Restrict the use of antibiotics in farming

Question 43

What is the problem of researchers developing new antibiotics

Answer 43

It takes a long time
Is extremely expensive
As new antibiotic resistant bacteria emerge all the time it’s unlikely we’ll be able to keep up

Question 44

What did Carl Linnaeus do

Answer 44

He classified living things into groups depending on their structure and characteristics

Question 45

What are the two kingdoms Linnaeus classified living organism into

Answer 45

The animal kingdom
The plant kingdom

Question 46

What are the categories Linnaeus divided living organism into

Answer 46

Kingdom
Phylum
Class
Order
Family
Genus
Species
(King Philip came over for good soup))

Question 47

What is the binomial name

Answer 47

The genus and the species

Question 48

Describe the impact of developments in biology on classification systems

Answer 48

We can now use microscopes to look at internal structures
We can also analyse an organisms biochemistry and look for similarities with other species

Question 49

What is the 3 domain system developed by Carl Woese

Answer 49

Archae-often found in extreme conditions
Bacteria-true bacteria
Eukaryote-which includes protists, animals, plants and fungi

Question 50

What are evolutionary trees

Answer 50

A method used by scientists to show how they believe organisms are related
They use current classification data for living organisms and fossil data for extinct organisms