Biology Paper 2

Gametes

Sex cells, sperm and egg. Chromosomes are single not paired. They are made by meiosis

Fertilisation

The fusion of the male and female gametes(sperm and egg). The genetic information gets mixed providing variation in the offspring

Asexual reproduction

Only one parent and produces genetically identical offspring (clones). No gametes involved so more energy and time efficient in favourable conditions. Increases the risk of exctitin

Sexual reproduction

1. Chromosomes are copied

2. Cells divide to form 4 daughter cells

3. Chromosomes are single

4. Cells are fertilised

5. The cell has chromosome pairs

6. Mitosis occurs to form an embryo

It provides variation and therfore provides a survival advantage

Malaria reproduction

In the human host malaria reproduces asexually. In a mosquito vector it reproduces sexually.

Fungi reproduction

Releases spores in air or water is asexually or can be sexually.

Plant reproduction

Sexually to produce seeds or asexually using runners or bulb division.

DNA

Determines our inherited structure and is found in chromosomes.

Gene

A small section of DNA on a chromosome. Encodes for a different amino acid and protein. The order of amino acids determines the shape and function.

Human genome

It is the entire genetic material that makes a human. Understanding it will allow us to search for certain genes linked to disease, understand inheritance and trace migration patterns.

Protein synthisis

How proteins are made. It has two parts transcription and translation.

Transcription

Happens in the nucleus. The base sequence is copied to a mRNA which leaves the nucleus

Translation

Happens in the cytoplasm. The mRNA attaches to a ribosome. tRNA brings amino acids which the ribosome puts together depending on the mRNA sequence. Chain folds up to form shape

Mutation

A change to the base sequence. Most of the time there is no effect, sometimes different amino acids are created so the genes doesn't do its fuction is is on when it shouldn't be

Alleles

Different versions of the same gene

Genotype

Tells us the alleles present in a person.

Ee = heterozygous ee = homozygous.

Phenotype

Tells us the characteristics caused by the alleles. A dominant allele will show in the phenotype even if there is only one copy

Cystic Fibrosis

Disorder of the cell membranes. Recessive conditions meaning you need a homozygous small pair to get it e.g. cc

Polydactyly

Have extra fingers or toes. Dominant condititon meaning you only need one big allele to get such as in a heterozygous pair e.g. Pp

Embryo Screening

Embryos are tested for certain conditions and only normal embryos are imprinted. It is very expensive, many embryos are destroyed and may lead to screening for desired characteristics such as intelligence or beauty.

Gender

xy = male xx = female

Variation

All the differences in the characteristics of individuals in a population. It is caused by a combination of alleles, the environment and mutations.

Evolution

The change in the inherited characteristics of a population over time through the process of natural selection.

Speciation

When two groups have become so different that they cannot interbreed to create fertile offspring as a result of geographical isolation.

Selective breeding

There are 4 reasons to selectively breed:

Gentle nature

More meat/milk

Larger fruits

Disease resistance

Select the two largest cows, breed them and repeat. May cause defects

Genetic Engineering

Identify the gene and isolate with enzymes.

Transfer to a vector (plasmid or virus)

Transfer gene into the desired organism at an early stage.

It may be harmful to crops and it may damage the environment but it can be used to treat disaese

Cuttings

1. Remove a small growing part (meristem at shoot)

2. Put it in rooting powder

3. Replant it

4. Grow the clone

Been used for 100 years

Tissue culturing

1. Divide plant into tiny pieces (a few cells)

2. Incubate cells with hormones

3. Must be sterile

It produces a lot of plants quickly and cheaply and can help to preserve rare species

Embryo cloning

1. Start with sperm and egg

2. fertilise

3. Allow to develop into an embryo

4. Split the embryo

5. Implant into surrogate mothers

All of the offspring will be the same

Adult cell cloning

1. Take a body cell and remove the nucleus

2. Take an egg cell and remove the nucleus

3. Put the body cell nucleus in the egg cell

3. Give the cell an electric shock so it splits

4. Insert the embryo that forms into a womb

Darwin

Studied fossils and geology to discover evolution by natural selection (the more adapted animals are more likely to survive). 1859 origin of the species..

People didn't agree because of strong religious beliefs, not enough evidence and no knowledge of genetics

Lamark

Thought giraffes stretched their neck and then it passed onto their offspring.

Wallace

Proposed the same theory as darwin

Fossils

Remains of organisms from millions of years ago which are found in rocks. They are formed when organisms don't decay, they are replaced by minerals or from footprints and roots.

Extinction

Happens as a result of

- a catastrophic event

- environmental changes

- new diseases or predator

- a more successful species

Antibiotic resistance

Random mutations make bacteria resistant to antibiotics. These bacteria survive and reproduce to form a resistant population. We should not over prescribe, restrict the use in farming and always complete treatments.

Carl Linnaeus

Developed a classification system.

Kingdom

Phylum

Class

Order

Family

Genus

Species

Carl Woese

Developed three domain system.

-Archaea (primitive bacteria)

-True bacteria

-Eukaryota

Homeostasis

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes

Automatic control system

Nervous or endocrine system

- receptor cells detect a stimulus

- they pass the information to the coordination centre

- the coordination centre processes the information

-instructions are sent to the effector

Nervous system

The CNS and other nerves. Electrical impulses are sent down neurons. Effectors are muscles and glands

Reflex actions

Help t protect us from danger

-Stimulus is detected by a receptor

-Electrical impulses travel along the sensory neuron

-At a synapse a chemical is released

-The impulse travels along the relay neuron

-It goes along the motor neuron to an effector

Practical: Reaction time

Person 1 drops a ruler and person 2 must catch it and measure the distance. Repeat.

You can measure on different people, the effect of practice or the effect of caffeine.

A computer is more accurate.