Biology

Drugs can be evaluated by comparing their beneficial and harmful effects, to decide which has the greater impact.

The impact of drugs

Many more people are treated in hospital for the effects of legal drugs, such as tobacco or alcohol, than for the use of illegal drugs. This is because there are many more people who smoke or misuse alcohol than people who take illegal drugs. So there will be more who suffer harm from tobacco than suffer from ilegal drugs.

This doesn't mean that illegal drugs are safer to use than legal (prescribed and non-prescribed) drugs. The proportion of illegal drug users who suffer harm is greater than the proportion of legal drug users who suffer harm.

Some types of drugs can affect sporting performance. Examples include:

STIMULANTS that increase the rate of body functions, such as heart rate

A faster heart rate delivers oxygen and sugars to muscles more quickly, so they can release more energy more quickly

ANABOLIC STEROIDS stimulate muscle growth.

Bigger muscles can help move bigger weights and generate more power, e.g. in weightlifting.

Drug bans in sport

Use of drugs to improve performance in sports competition is considered UNETHICAL.

Reasons for this include:

• side effects of the drugs can harm athletes
• the drugs may give an unfair advantage over athletes who don't use them.

Organisms need a supply of materials from their surroundings, and sometimes from other living organisms, so that they can survive and reproduce. This means there is COMPETITION between organisms for materials that are in limited supply.

Competition between plants

• Competition for light and space
  
• Competition for water and nutrients

Competition between animals

Animals may compete with each other for:

• food
• mates for reproduction
• TERRITORY (space for feeding, reproduction and rearing young).

You will be expected to know the factors that organisms are competing for in an example.

All organisms (including micro-organisms) have ADAPTATIONS that help them to survive the conditions of the environment in which they normally live.

Animals in the Arctic

Factors in the environment affect living organisms and their DISTRIBUTION (how widely spread they are). Changes in these factors may change their distribution.

Environmental factors

Living factors, e.g.

• prey
• competitor
• predator

Non-living factors, e.g.

• light
• average temperature
• average rainfall
• oxygen levels in water
• pollution

Changes in these factors can affect organisms.

Genes, chromosomes and nucleus

• Different genes control the development of different CHARACTERISTICS of the body.

REPRODUCTION is the production of new individuals. There are two forms of reproduction.

Sexual reproduction

• gamete from mother fuses (joins) with gamete from father
• mixes genetic information from each parent
• offspring have different combinations of genes, so show variety in characteristics

Asexual reproduction

• no fusion of gametes - only one parent
• no mixing of genetic information
• all offspring have same genes as parent and each other

Clonesare individuals with identical genes.

There are several modern techniques for cloning organisms.

Tissue culture

Plant tissue is like taking plant cuttings, but with very small pieces that contain just a few plant cells. The new plants are all clones because their cells contain the same genes as the parent plant.

Embryo transplants

Splitting embryos makes it possible to produce small numbers of clone animals at the same time. This is most often done with high-quality farm animals.

Adult cell cloning

Genetic engineering produces GENETICALLY MODIFIED (GM) organisms.

GENETIC ENGINEERS is the transfer of a gene from one organism to a different organism so that the desired characteristic is produced in that organism.

Genes can be transferred from any kind of organism to any other kind of organism, e.g. bacteria, humans, other animals, plants.

• The gene for a characteristic is 'cut out' of a chromosomes using enzymes
• The gene is inserted into a chromosome inside the nucleus of a cell in a different organism
• the cell of this organism now produces the characteristic from the gene

GM crops

GM CROP plants have been genetically modified to give them new characteristics, such as:

• resistance to attack by insects
• resistance to HERBICIDES, so that fields can be sprayed to kill weeds, but not the crop.

New scientific developments cause new issues that we need to think about. To make good judgements about these developments we need good information.

Economic issues:

related to money

Judgement: Is it worth the cost?