SB4 - Natural selection and genetic modification

What is Darwin’s theory of evolution by natural selection?

1. There is variation within a species due to mutation, which causes animals in the species to have different characteristics.

2. Individuals with characteristics best suited for the environment will survive more easily and breed successfully. This is called natural selection.

3. These characteristics are then passed to their offspring and so the characteristics survives and over many generations, the entire species will have the characteristic.

Who was the oldest human fossil and how old?

Ardi was 4.4 million years old

Who is the next oldest human fossil and how old?

Lucy is 3.2million years old

How old was the oldest homo erectus ever found?

1.6 million years old. Discovered by Richard Leakey.

What is another piece of evidence for human evolution?

The development of tools since they became sharper and more complex the closer to present time they were, suggesting that humans became smarter.

How can tools be dated?

They are dated approximately, using radiocarbon dating or by assuming the tools are as old as the rock layer which surrounds it.

How does the pentadactyl limb provide evidence of evolution?

Since many animals share similar limb bone structures, providing evidence for evolution.

How did genetic analysis lead to suggestion of the three domains?

Genetic analysis lead to the discovery of some organisms having unused portions of DNA like the Eukaryota but also had no nucleus like bacteria. So a new form of classification had to be invented to place the Archaea organisms.

What is selective breeding?

Selective breeding is when farmers select the animals with the most desirable characteristic of a species and breed them together. Then select the offspring with the most desirable characteristic and breed them and do this over and over again until all the species has the desired characteristic.

Describe the process of tissue culture.

1. Take the plant that you would like to clone e.g. a plant with a desirable characteristic.

2. Remove a piece of tissue from the root or tip.

3. Using aseptic techniques using an autoclave (sterile conditions). Place tissue in a special growth medium.

4. Once tissue is developed, transfer it to compost for further growth.

Benefits of tissue culture.

Produces lots of offspring with a desirable characteristic.

Increases number of crops resistant to bad weather and can increase crop yield.

Risks of tissue culture.

The gene pool is reduced so disease could easily spread through the species.

Clones tend to have low survival rates.

What is genetic engineering?

Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.

What are the stage of genetic engineering?

1. Genes from chromosomes are ‘cut out’ using restriction enzymes, leaving sticky ends

2. Using same restriction enzymes cut the vector, leaving sticky ends (such as bacteria plasmid) into which the genes will be placed.

3. Ligase is used to attach the sticky ends of the gene and the plasmid together to produce a recombinant gene.

Advantages of GMO’s

1. Useful to mass produce certain hormones in organisms.

2. Can be used to improve growth rates, allow crops to grow in harsh conditions and to make crops herbicide resistant.

3. Increases the crops nutritional value by causing them to produce vitamins.

4. Increases yield

Disadvantages of GMO’s

1. Effects of GM crops on the human body are unsure.

2. Herbicide GM resistant crops could cause weeds to become herbicide resistant through cross-pollination.

What are 2 agricultural solutions and explain them?

1. Fertilisers - provide useful nutrients such as ( nitrate and phosphates) making the plant grow faster and larger, increasing yield.

2. Biological control - Use of a species to control the population of another species which damages and decreases the yield of the plant.

Advantages and Disadvantages of selective breeding.

Adv -Increases yield of a product from the organism. 

Can be bred to be resistant to particular diseases, increasing yield

Disadv - Can cause severe health problems in the offspring.

Lack of genetic variation, so they have a smaller gene pool so a disease could cause a great amount of the population to be wiped out.