Variation and evolution

What is variation?

The differences in the characteristics of individuals in a population

What are the three main causes of varation?

• Alleles individuals have inhereited - genetic

• Enviroment

• A combination of genes and the enviroment eg height (genetics on how tall we can grow and enviroment on how much calcium we coonsume)

What are mutations?

Random changes to DNA

What is a phenotype?

The observable characteristics of an organism, resulting from its genotype and interactions with the environment

What can mutations lead to?

New phenotypes (adapt)

What is evolution?

The change in the inherited characteristics of populations over time through the proccess of natural selection

What are the step of evolution in natural selection?

• Every organism has a slightly different combination of alleles that is inherited from its parents

• This means some organisms in the same species are better adapted to certian conditions then others

• If there is a sudden change in the enviroment, organisms which have inhereited alleles that suite the enviroment will survive and reproduce while other who havent got this enviroment die

• This means their offspring may inherit the desiered allele and go on to live

• Over generations this allele will pass down the generations

What can evolution lead to?

A species spliting off into two species as their alleles become to different

If the two species were to reproduce they would produce unfertile offspring

Why may a organism be selectivly bread?

• To create a gentle nature

• To become disease resistance

• More food to be produced

• To make flowers larger or unusal flowers

How is selective breading carried out?

• Take a mixed population of the organism and choose two with the most presented wanted characteristics

• Breed them together

• The offspring will be a mixture of the two meaning the wanted characteristic is dominant

• This is carried over many generations

What are the problems with selective breeding?

• If we breed together closely related animals or plants it produces interbreeding

  • This can cause them to be prone to disease and inherited defects

What are genes? What do they do?

• Genes are sections of DNA on a chromosome

• Each gene codes for the amino acid sequence of a specific protien

What happens in genetic engineering?

Genes from one organism are cut out and transfered to cells of a different organism

What happens in genetic engineering?

• Genes from one plants are cut out and transfered to cells of a different plants to make genetically modified crops

• This produces a greater yield than normal crops

• This is done to make plants more resistant or bigger

What is geno therapy?

The use of genetic modification as a way to treat inherited disorders in humans

What are the main steps in genetic engineering?

• First identify the gene we want to transfer

• Use enzymes to isolate this gene

• Transfer the gene into a small circle of DNA called a plasmid (origanily came from bacteria and are useful for transfers) or we can use a virus - these are vectors

• The desired gene is transferred into the cells of the target organisms

What is a important point on genetic engineering?

Always transfer the gene at an early stage in the organisms development so all the cells recieve the gene

What are fossils?

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

What are the three ways fossils can form?

• Fossils can form when parts of organisms have not decayed which happens when the conditions for decay are absent eg if its too cold

• A fossil can form even if the organism decays if parts of the organisms are slowly replaced by minerals during the decay process

• Fossils can be the preserved traces of organsims such as footprints and preserved place where roots were

What are the problems with fossils?

Many of the earlist forms of life were soft-bodied organisms so had no shell or skeleton

What do fossils show?

Species that have became extinct

Why do species become extinct?

• Due to a catastrophic event

• Enviroment changes

• New predators

• New diseases

• A species become extinct if a new, more succesful species involves and competes with it for food or water

What organism evolves rapidly and why is this?

• Bacteria

• This is because it can reproduce every thirty minutes

What kills bacteria?

Antibiotics

Other then for humans, what is antibiotics used for?

To prevent diseases in animals

What is MRSA?

A common strain of antibiotic resistant

How does antibiotic resistance happen?

• A mutation can make a bacterium resistant to antiobiotics in a group of bacteria

• When antibiotics are used on these groups of bacteria all the bacteria get killed apart from the bacterium that is resistant to antibiotics

• This bacterium survices and reproduces without competition from other bacteria and other time the resistent strain rises

• The resistant strain now spreads and there is no longer effective treatment

How can we reduce the spread of resistant bacteria?

• Doctors should prescribe antiobiotics appropriately

• Patients should complete their course of antibiotics

• Restrict the use of antibiotics in farming

Whats the problems with developing new antibiotics?

• Expensive

• Time consuming

How are organisms classified?

Organisms are classified into species based on their structure and characteristics

How did Linneaus classify organisms?

• Firstly he organised them into two kingdoms

  • Animal and plant kingdom

• He then divided each kingdom into smaller categories

What are the catergories? (Using a abrevation)

Kingdom - King

Phylum - Philip

Class - Came

Order - Over

Family - For

Genus - Good

Species - Soup

What is the binomial name?

The mixture of the genus and the species

What advances have been made for these catergories?

Microscopes can be used now to examine the internal structure and DNA not the internal structure

Whats the three domain system?

• Archae

  • Found in extreme hot conditions

• True bacters

  • Eg the kind that live in the human digestive system

• Eukaryote

  • This includes animlas, plants and fungi (and protist)

What are the function of evolutionary trees? How are they made?

• Show how closely related organisms are to each other

• They are made using classification data on living organsims eg their DNA

• However they use fossils for extinct animals

Why can using fossil records for evolutionary trees be a problem?

Fossil records of a species may be incomplete

Example of a evolutionary tree