10 Genes Flashcards
Evolution
Theory that animal and plant species living today descended from species that existed in the past
Natural selection
Process by which species change over time in response to environmental changes and competition for resources. The organisms with the characteristics that are most suited to the environment survive and reproduce, passing on their genes
How and when did evolution start?
Started with unicellular animals that lived in water 3 billion years ago
There are two types of hover fly (A and B, B looks like a wasp), they are both eaten by a predator, but the predator doesn’t eat wasps. Explain in terms of natural selection which is more likely to survive
- The two flies show lots of variation
- Hoverfly B looks like a wasp (mimicry)
- Hoverfly B is less likely to be eaten and more likely to survive and reproduce
- Hoverfly B passes on their genes and characteristics to their offspring
Fossils
- The remains or traces of plants and animals that have turned to stone
Describe how 2 squirrel species could have had the same ancestor species
- There was lots of variation within the original ancestor species
- Two populations of the ancestor species became geographically separated
- Squirrels with the characteristics best suited to the environment survive and reproduce
- Over many generations the 2 populations will become so genetically different they are considered different species
_____
A
B
Suggest which fossil is older and explain why
- Fossil b is likely to be older because it is buried under much more earth
- Could take 10,000 years for that much earth to be on top of it
- Fossil A is much nearer to the surface so it died later
Fossil A and B are structurally very similar, why?
- The conditions in the environment (water availability, temperature etc stayed the same)
- The adaptations that fossil B had were already suited to the environment
- Little change in environment = slow evolution
Peer review
The evaluation of a scientist’s work by another scientist
What does Darwin’s theory state?
Organisms evolve as a result of natural selection
When was Charles Darwin born?
1809
What did Charles Darwin and A_______ R________ W_______ do in 18_8?
Published a paper together
What did Darwin publish in 185_?
9
Controversial book ‘On the Origin of Species’
Describe three pieces of evidence that support Darwin’s theory of evolution.
- Fossil records indicate that organisms have changed over time
- Changes observed in the microorganism population eg the development of antibiotic resistant bacteria
- Extinction of species show that organisms that do not adapt to their changing environment will die out
Describe how Darwin’s communications with Wallace resembles the peer review process of modern science.
- Darwin and Wallace recorded their findings separately at different locations
- They communicated these findings to each other
- It was only when their ideas agreed that the results were published
Extinct
When no more individuals of a species remain anywhere in the world
Competition
When two or more living things struggle against each other to get the same resource
Biodiversity
A measure of the variety of all the different species of organisms of Earth or within a particular ecosystem
Population
Groups of organisms of the same kind living in the same place
When will a species become extinct?
When it’s not adapted to its environment
Name five factors that can cause a species to become extinct
- Changes to the organism’s environment
- Destruction of habitat
- Outbreak of a new disease
- Introduction of new predators
- Increased competition for resources
Explain how a lack of biodiversity can affect an ecosystem
- If an area has a low biodiversity only a small number of species will be present, as a limited supply of food/shelter is provided.
- The ecosystem is unstable, because if this food source is lost through disease/fire/environmental factors and an alternative species is not present to eat, all organisms may die
Endangered species
A species with only a small numbers of organisms left in the world
Conservation
Protecting a natural environment, to ensure habitats are not lost
Gene bank
A store of genetic samples, used for research and to try and prevent extinction
Captive breeding
Breeding animals in human-controlled environments
What do captive-breeding programmes aim to achieve?
- Create a stable, healthy population of species
- Gradually re-introduce the species back into its natural habitat
What are the disadvantages of captive breeding?
- Maintaining genetic diversity can be difficult. Only a number of breeding partners are available
- Organisms born in captivity may not be suitable for release in the wild
What are the advantages of conservation?
- Reduced disruption to food chains and webs
-Makes it possible for medicinal plants to be discovered
What are the UK conservation areas called and what percentage of land do they cover?
SSSIs (Sites of Special Scientific Interest), 8%
Seed banks
Dried seeds of plants are stored at low temperatures
Tissue banks
Buds and other cells from plants are stored
Pollen banks
Pollen grains are stored
Cryobanks
A seed or embryo is preserved at a very low temperature (normally in liquid nitrogen). Sperm and egg cells can also be preserved in this way
Name the four types of gene banks
- Seed banks
- Tissue banks
- Pollen banks
- Cryobanks
DNA
(Deoxyribonucleic acid) A molecule found in the nucleus of the cell that contains genetic information
Inherited characteristics
Features that are passed from parents to their offspring
Chromosome
Thread-like structure containing tightly coiled DNA. It contains many genes.
How many chromosomes do humans have?
46 (23 pairs)
Gene
A section of DNA that determines an inherited characteristic
How many genes does each chromosome contain
1000s
How does a human get 46 chromosomes?
- The egg and sperm cells only have one copy of each chromosome
- During fertilisation, the egg and sperm cells join together
- When the nuclei join, their chromosomes pair up, producing an embryo with 46 chromosomes
Mutation
Change to the DNA that can cause disease
What can happen if a change occurs in a gene?
- It can affect the organism’s characteristics
- The body normally detects these changes and tries to mend them
- If undetected they can cause disease
What happens if a mutation occurs in a gamete cell?
- The altered form of the DNA may be passed onto the organism’s offspring
Give an example of a beneficial genetic mutation
In some species of bacteria mutation has resulted in them becoming resistant to antibiotics p
What are the three main features of the DNA?
- Made up of two strands
- The strands are joined together by four different chemicals called DNA bases A, T, C, and G
- Strands are twisted together to form a double-helix shape
Explain how scientists worked together to discover the structure and function of the DNA (6 marks)
Early work by Mendel led to the discovery that certain characteristics can be passed from parents to offspring. Miescher identified ‘nuclein’ in the nucleus of the cell. Nuclein is now called DNA.
Avery transferred DNA between bacteria, transferring characteristics in the process. This proved that genes are sections of the DNA molecule.
Chargaff’s work showed that all DNA molecules contain equal quantities of bases in their respective pairs (number of A = number of T, number of C = number of G).
Wilkins and Franklin then used X-rays to take an image of DNA crystals.
Watson and Crick built on the evidence gathered by a number of other scientists. This helped them to produce the double-helix model of the DNA molecule.
Alleles
Different forms of a gene
Dominant (allele)
A dominant allele will always express itself if present
Recessive (allele)
Will only be expressed if two copies are present
How many genes do you have for each characteristic?
2 (one from mum and one from dad)
Punnet square
A diagram used to show the possible combinations of alleles inherited from parents
Explain why offspring from the same parents look similar but are not usually identical
They both inherit genetic information from both parents, but during fertilisation genetic material from the parents is mixed. Each inherit a different combination of genes.
Genetic modification
(Also called genetic engineering) A technique in which scientists insert foreign genes into organisms to change their characteristics
Describe the advantages of genetic modification over selective breeding
Genetic modification is much more precise than selective breeding, it is a much quicker process, and it can alter characteristics more dramatically, for example, making fish glow in polluted water.
Explain how an organism’s genes are altered
-To create an organism with a desired characteristic, scientists take genes from another organisms that shows this characteristic
- Foreign genes are put into the plant or animal cell at a very early stage in the organism’s development
- As the organism develops, it will display the characteristics of the foreign gene
Why is bacteria genetically modified?
Bacteria can be genetically modified to produce many useful chemicals such as vaccines and antibiotics. Bacteria reproduce very quickly so large amounts of the chemical can be made in a very short period
Suggest 2 arguments for and 2 against genetic engineering.
- To produce crops of higher yield, to produce disease-resistant crops
- Interfering with organisms against their will, may increase allergies, can lead to unwanted cross breeding
State and explain two reasons that could cause an animal to become extinct
The introduction of new predators can mean more organisms in a species are eaten than number of offspring produced. Destruction of habitat can mean loss of shelter for organisms, which leads to the death of individuals through exposure
Describe the role of gene banks in helping prevent extinction
Gene banks store genetic samples, for example, seeds/eggs/sperm/tissue. Samples from gene banks can be used to create new organisms in the future. Samples can also be used for research.
Explain the process of natural selection and the role it plays in the evolution of species
Organisms evolve through natural selection slowly over time. Organisms in a species show variation – this is caused by differences in their genes.
The organisms with the characteristics that are best adapted to the environment survive and reproduce.
Less well-adapted organisms die.
This process is known as ‘survival of the fittest’.
Genes from successful organisms are passed to the offspring in the next generation.
This means the offspring are likely to possess the characteristics that made their parents successful.
This process is then repeated many times.
Over a long period of time this can lead to the development of a new species.
Explain how a lack of biodiversity can affect an ecosystem and why helping to preserve biodiversity can benefit humans.
• Biodiversity is a measure of the variety of all the different species of an organism present in an area
- Low biodiversity means not many species are present
- Limited food/shelter present
- Unstable ecosystem/less stable, as, if food source is lost through disease/fire/environmental factor, all organisms may die
- Preserving biodiversity ensures different species survive
- May provide new drugs
