Biology 1b

Animals that live in hot, dry conditions need to keep cool and use water efficiently. Large surface area to volume lets desert animals lose more body heat, which stops them from overheating.

1. Desert animals lose less water by producing small amount of concentrated urine, they also make very little sweat. They have thin laers of fat and a thin coat. A sandy colour gives good camouflage toavoid predators.

Arctic animals live in really cold conditions and need to keep warm. They have a compact shape to keep their surface area to a minimum which reduces heat loss.

The have a thick layer of blubber for insulation, which also acts as an energy store. Thick hairy coats keep body heat in and grasy fur sheds water which prevents cooling. The have white fur to help avoid predators.

Desert plants have adapted to having little water. Plants lose water vapour from the surface of their leaves, cacti have spines instead of leaves. The also have a small surface area compared to their size which also reduceswater loss. It stores water in its thick stem. They have shallow but extensive roots to absorb water quickly.

There are various feautres used by animals and plants to protect them against being eaten.

Some plants have armour, like roses(thorns), cacti(sharp spikes) and tortoise(shell).

Others produce poisons like bees and poison ivy.

Some have warning colours like wasps.

Some microorganisms are known to adapt to live in extreme conditions like super hot or high pressured areas.

Organisms need things from the environment and other organisms to survive and reproduce:

Plants need light, space, water and minerals(nutrients from the soil). Animals need spaces, food, water and mates. They also compete with one anotherfor the same resources.

Environmental change:living factors: a change in the; occurence of infectious diseases, numbers of predators, number of prey, availability of food sources and the number of competitiors.non-living facotrs: a change in the; average temperate, average rainfall or in the level of air or water pollution.

Population increase: if the number of prey increase, theres more food so more chance of survival and reproduction so numbers increase.

Population decreases: some pesticides may have a ngeative effect, theres less food available or theres more diseases.

Population distribution change: it means where an organism lives. e.g the distribution of bird species in Germany is changing because of a rise in temperature.

Environmental change is measured in living indicators:some organisms are sensitive to changes in their environment, they are known as the indicator species. Air pollution can be monitored by looking at a certain type of lichen that are sensitive to the concentration of sulfur dioxide. The air is clean if there are lots of lichen. Some ivertibrates like mayfly are good indicators of water pollution because it's sensitive to the concentration of dissolved oxygen, if theres mayfly then the water is clean. Others have adapted to living in polluted conditions, rat-tailed maggots or sludgeworms indicate a high level of water pollution.

Measured in non-living indicators:they use satellites to measure the temperature of the sea surface and the amount of snow coverage. Automatic weather stations tell us atmospheric temperature at various locations. They measure rainfall using rain gauges to find out the average rainfall year on year. And they use dissolved oxygen meters to measure the concentration of dissolved oxygen in water to discover changes in water pollution.

There's less energy and less biomass every time you move up a stage in a food chain. Theres usually fewer organism when you go up as well.

Each bar on the pyramid shows the mass of living material at that stage. Basically how much the organisms would weigh if you put them all together. The big bar along the bottom would be the primary consumer and then the secondary consumers and so on.

Energy from the sun is the source of energy for nearly all of life. Green plants use a small amount of the suns energy during photosynthesis, the energy is stored in the cells of plants and works its way up the food chain.

Respiration supplies energy for all life processes including movement. Most energy is lost to the surroundings as heat.

Some of the material that makes up plants is inedible so it doesn't pass on to the next stage of the food chain.

This explains why you get biomass pyramids, most of the biomass is lost so it doesn't become biomass in the next level up.

It also explains why there's hardly any food chains with more than four or five stages because so much energy is lost at each stage.

Living things are made of materials they take from the world. Plants take elements like carbon, oxygen, hydrogen and nitrogen from the soil and air. They turn these elements into complex compounds that make up living organisms.

The elements are returned to the environment in waste products produced by the organisms or when they die. The materials decay because theyare broken down by microorganisms.

Microorganisms work best in warm, moist conditions. Many break material down faster when theres plenty of oxygen available.

All the important elements are recycled and returned back to the soil ready to be used by new plants.

The material that is taken out of the soil is balanced by those that are put back in.

It shows how carbon is recycled. The whole thing is powered by photosynthesis, where carbon dioxide is removed from the atmosphere and the carbon is used to make carbohydrates, protein and fats in the plants.

Some of the carbon is returned when the plants respire, but the carbon carries on throught the food chain. Some of the carbon is returned when the animals repsire.

When plants and animals die other animals (detrius) and microorganisms feed on the remains . When these organisms repsire more is returned.

Animals also produce waste which is also broken down by detrius feeders, compounds from the waste are taken up by the soil and plants and are put back in the food chain.

Carbon dioxide is also released by hte burning of wood and fossil fuels. So the carbon is constantly being cycled from the air, through food chains and back into the air again.

Organisms of the same species have differences. There are two types of variation: genetic variation and environmental variation.

Different genes cause genetic variation:all plants and animals have some similar and some different characteristics to their parents. An organisms characteristics are determined by the genes inherited.  The genes are passed on in sex cells. Most animals get some genes from the mother and some from the father.

Characteristics are also influenced by the environment: environmental variation covers a wide range, basically any difference that has been caused by the conditions something lives in, is an environmental variation.

Most cells in the body have a nulceus, which containsyour genetic material in chromosomes.

Humans have 23pairs of chromosomes.

Chromosomes carry genes. Different genes control the development of different characteristics.

A gene is a short length of a chromosome, which is quite a long length of DNA.

The DNA is coiled up to form the arms of the chromosome.

There can be different versions of the same genes which give different versions of a characteristic, like eye colour. The different versions of the same gene are called alleles.

Sexual reproduction is where genetic information from two organisms, the mother and the father, is combined to produce offspring which are genetically different to either parent.

The mother and father produce gametes, the egg and sperm cells.

Each gamete contains 23 chromosomes, half the number than in normal cells, instead of having two of each, gametes just have one.

The egg and the sperm cell then fuse together to form a cell with full number of chromosomes.

This is why the offspring inherits features from both parents receiving a mixture of chromosomes. This mixture of genetic material produces variation in the offspring.

An ordinary cell can make a new cell by dividing in two. The new cell has exactly the same genetic informationas the parent, it's known as asexual reproduction.

There is only one parent, there's no fusion of gametes, no mixing of chromosomes and no variation. The offspring are genetically identical to the parent, they're clones.

X-shaped chromosomes have two identical halves. So each chromosome splits down the middle to form two identical sets of kalf-chromosomes.

A membrane forms around each set and the DNA replicates itself to form two identical cells with complete sets of x-shaped chromosomes.

This is how all plants and animals grow and produce replacement cells.

Some organisms also produce offspring using asexual reproduction like bacteria and certain.

Plants can be cloned from cuttings and by tissue culture. Gardeners take cuttings to produce genetically identical copies, these plants can be produced quickly and cheaply.

Tissue culture is where a few plant cells are put in a growth medium with hormones, which grow into new, clones of their parents. They can be made quickly in very little space and can be grown all year.

Farmers can produce cloned offspring using embryo transplants. Sperm cells are taken from a prize bull and egg cells are taken from a prize cow. They are then used to artificially fertilise an egg. The embryo develops, splits many times to form clones. These cloned embryos can then be implanted into lots of other cows where they grow calves which will all be genetically identical to each other.

Adult cell cloning involves taking an unfertilised egg cell and removing its genetic information. A complete set of chromosomes from an adult body cell is inserted into the empty egg cell. The egg is then stimulated by an electric shock to make it divide. When the embryo is a abll of cells, it's implanted into an adult female to grow the genetically identical copy of the original adult.

Cloning could be used to protect endangered species.

Some people worry that humans may be cloned in the future, if it was allowed it could result in severly disabled children.

Genetic egineering uses enzymes to cut and paste genes. The idea is to copy a useful gene from one organism'schromosome into the cells of another.

 A useful gene is cut from one organisms chromosome using enzymes.

Enzymes are then used to cut another organism's chromosome and then to insert the useful gene. Scientists use this method to do lots of different things.

Genetically modified crops have had their genes modified to make them resistant to viruses, insects or herbicides.

Sheep have been genetically engineered to produce substances, like drugs, in their milk can be used to treat human diseases.

Genetic disorders like cystic fibrosis are caused by faulty genes. Scientists are trying to treat these disorders by inserting working genes into sufferers, it's called gene therapy.

Genetic engineering has the potential for solving man problems, treating diseases, more efficient food production etc. There are worries about long-term effects, that changing someones genes could create problems, that could get passed onto future generations.

Pros: GM crops can increase the crop yield making more food. People in developing countries often lack nutrients, GM crops could be engineered to contain nutrients thats missing. GM crops are already being grown elsewhere in the world without problems.

Cons:people say that growing GM crops will affect the number of weeds produced by flowers, which can reduce farming biodiversity. Not everyone things they're safe and peopleare worried that they will develop allergies. A big concern is that transplanted genes may get out into the natural environment.

The theory of evolution is that 3billion years ago, life on earth was simple organisms, from which complex organisms evolved.

Organisms have similarities and differences which allow us to classify them:plants make their own food and are fixed in the ground. Animals move about and can't make their own food. Microorganisms are different to plants and animals.

Species with similar characterisitics usually have similar genes because they share a common ancestor,so they're closely related.

Occasionaly genetically different species might look alike too, it could be the way they're adapted to the same habitts.

Evolutionary trees show common ancestors and relationships between organisms. The more recent the ancestor, the more closely related.

Darwin came up with the theory of evolution. Individuals with characterisitics best adapted to the environment have a better chance of survival so they are more likely to breed successfully. So the useful genes are passed on to the next generation.

A mutation is a spontaneous change in a gene. They can be beneficial by producing a useful characteristic, which gives the organism a better chance of survival. Therefore it's more likely to be passed on to future generations.

It went against religious beliefs about how life on earths developed. There wasn't enough evidence and no one had the knowledge of genes or mutation.

Now there is so much evidence that Darwins theory is an accepted hypothesis.