Cycle test 3 revision

Heredity

The process by which genetic material is passed from one generation to the next.

DNA

Deoxyribonucleic acid, the genetic material of the cell.

Chromosome

Long thin strands of DNA found in the nucleus.

Gene

Part of a chromosome which determines a particular body characteristic e.g. eye colour.

Allele

Different versions of the same gene e.g. the gene which codes for blue eyes (b) is an allele of the gene which codes for brown eyes (B).

Dominant

Allele which can control the development of a characteristic when it is present on only one chromosome (e.g. B) .

Recessive

Allele which controls the development of a characteristic only if the dominant allele is not present (e.g. b).

Natural selection

When an individual is more likely to survive and breed due to the variation in their genes making them more successful than other individuals.

Extinction

The loss of all living representatives of a species.

Species

Individuals belong to the same species when they can breed together to produce fertile offspring.

Biodiversity

The range of living species of organisms in an area.

Four key scientists involved in the development of the DNA model:

Rosalind Franklin

Francis Crick

James Watson

Maurice Wilkins

The role Rosalind Franklin played in the development of the DNA model:

Took the picture.

The roles Francis Chick and James Watson played in the development of the DNA model:

Provided the sketch.

The role Maurice Wilkins played in the development of the DNA model:

Showed Francis Chick and James Watson the picture giving them the ability to write and submit a paper.

The scientists that received the Nobel Prize for their work:

Maurice Wilkins

James Watson

Francis Crick

The year in which the scientists received the Nobel Prize for their work:

1962.

The colour of chromosomes are:

Colourless.

Chromosomes are made of a material called:

DNA.

Chromosomes are found in the:

Nucleus of a cell.

Most of our cells have:

46 chromosomes.

Our 46 chromosomes are arranged as:

23 pairs.

You get one of each pair of chromosomes from:

The egg (mother).

You get the other one of each pair of chromosomes from:

The sperm (father).

Each chromosome has many instructions along its length. These instructions are called:

Genes.

They control the development of a characteristic e.g. eye colour and so provide a blue print for your body. These are called:

Genes.

Our cells have… copies of each chromosome.

2.

We have… copies of each gene.

2.

Sometimes the copies of each gene is identical, but sometimes the copies are identical, but sometimes they are present are different versions called:

Alleles.

One version of a gene may be… compared to the other. This will be the version that determines the characteristic.

Dominant.

The other allele that doesn't determine the characteristics is called:

Recessive.

When a sperm and an egg are made each one just gets… copy of each chromosome.

1.

Each sperm/egg has just one copy of each…

Gene.

Which copy of each gene a sperm or egg gets is…

Random.

When an egg gets fertilised by a sperm we now have… copies of each chromosome again.

2.

There are… chromosomes in total.

46.

There are… pairs of chromosomes in total.

23.

XY is…

Male.

XX is…

Female.

A red blood cell does not have a…

Nucleus.

If people have 3 21 chromosomes then they have…

Down syndrome.

Chromosomes are only visible when…

Cell is dividing.

Fertilised sperm + egg =

Zygote.

A species is…

A group of individuals that can breed together to produce a fertile offspring.

Variation is…

No two organisms look or behave exactly the same. They vary.

The two causes of variation are…

Genetic variation and Environmental variation.

Genetic variation is…

All animals and plants have different genes. These are codes which determine how the organism will develop.

Variation can be described in two ways which are:

Continuous variation and Discontinuous variation.

Continuous variation means:

The feature can vary over a continuous range of values (e.g. height - you can be any value within a certain range).

Discontinuous variation means:

This feature can only take one of several categories (e.g. eye colour could be blue, brown, green or grey).

Eye colour is:

Genetic variation only.

Natural hair colour is…

Mixture of genetic and environmental variation.

Dyed hair colour is:

Mixture of genetic and environmental variation.

Shape of nose is:

Mixture of genetic and environmental variation.

Blood group is:

Genetic variation only.

Academic prowess is…

Mixture of genetic and environmental variation.

Attached/free ear lobes is…

Genetic variation only.

Condition of teeth is…

Mixture of genetic and environmental variation.

Body mass is…

Mixture of genetic and environmental variation.

Colour of lipstick coated lips is…

Mixture of genetic and environmental variation.

Ability to roll your tongue is…

Mixture of genetic and environmental variation.

Muscle size is…

Mixture of genetic and environmental variation.

Height is…

Mixture of genetic and environmental variation.

… was suggested 150 years ago by Charles Darwin.

Natural selection.

Step 1 of Natural selection:

Animals and plants are always in competition with each other.

Step 2 of Natural selection:

Sometimes an individual gains an advantage in the competition.

Step 3 of Natural selection:

This might be against other species or other members of its own species.

Step 4 of Natural selection:

That individual is more likely to survive and breed.

Step 5 of Natural selection:

This is known as Natural selection.

The first person to describe natural selection as survival of the fittest was:

Charles Darwin.

Step 1 of Survival of the fittest:

Individuals in a population have variations in their characters caused by variations in their alleles (versions of their genes)

Step 2 of Survival of the fittest:

These variations are caused by mutations in their DNA. Mutations happen randomly and sometimes cause a gene to change in a beneficial way.

Step 3 of Survival of the fittest:

If the environment where a population is living changes, some individuals may be better able to survive in the new conditions than others (due to their different characteristics caused by their mutated DNA).

Step 4 of Survival of the fittest:

These individuals survive longer than the others (survival of the fittest).

Step 5 of Survival of the fittest:

They breed and pass on their successful alleles (their versions of the genes) to their offspring.

Step 6 of Survival of the fittest:

If this continues, over time, new species can be formed as the population is now so different from the previous population so they can no longer breed to produce fertile offspring.

Dodos evolved from..

Pigeons.

Pigeons are..

Small, agile, fast flier.

Dodos are..

Large, slow, flightless.

Step 1 of how dodos evolved from pigeons:

The pigeons were all slightly different from each other (they showed natural variation) due to their genes having slightly different alleles.

Step 2 of how dodos evolved from pigeons:

This meant some birds had smaller wings.

Step 3 of how dodos evolved from pigeons:

These birds were all able to compete well with other pigeons - they did not need large wings as the food was on the ground and there were no predators to fly away from.

Step 4 of how dodos evolved from pigeons:

Some birds had larger bodies.

Step 5 of how dodos evolved from pigeons:

These birds could compete well in times when food was scarce as they had larger reserves of energy.

Step 6 of how dodos evolved from pigeons:

Successful (fittest) birds survived and reproduced, passing on the alleles that caused them to have small wings and larger bodies to their offspring.

Step 7 of how dodos evolved from pigeons:

Over time the birds changed so that they looked like dodos instead of pigeons.