B2

Classification can change over time. To begin with there where only two kingdoms: Plants and Animals.

There are now five:

• Monera-Single celled; Has cell wall; No nucleas; No chloroplasts. - Absorb nurtients, cell wall, or produce their own. - May/May not move
• Protista-Single celled; No cell wall; Has nucleas; Some have chloroplasts. - photosynthesis or ingestion of other organisms or both. - Move using cillia or flagella
• Fungi-Multi celled; Has cell wall;  Has nucleas; No chloroplasts. - Get nutrients through decaying material. - Cannot move
• Plants-Multi celled; Has cell wall; Has nucleas; Has chloroplasts. - use sunlight for photosynthesis. - Most don't move.
• Animal-Multi cell; No cell wall; Has nucleas; No chloroplasts. - Get nutrients ingestion. - using cillia, flagella or muscles.

This classification system will need to be changed as more species are found and new discoveries, especially in genetics, are made.

Some organisms from seperate species can mate. The ofspring is called hybrids. Hybrids can never be fertile so they cannot be classed as a new species.

Classifying some organisms e.g. those in a micro-enviroment, can be difficult. The variety of life is a continuous spectrum which makes it difficult to place some organisms into distinct groups. Organisms that only reproduce aseually can be hard to classify. Organisms are constantly changing to suit their enviroment.

Evolutionary relationship between organisms in the kingdoms can be displayed in evolutionary trees. The theory all scientists agree on:

• Monera represent the earliest group of organisms.
• Monera gave rise to protista, from which the three other kingdoms evolved along seperate lines (fungi, plants, animals).

The five kingdoms are split into phyla. Each phylum is divided into classes; each class into orders; each order into families; each family into genera; each genus into species. Members of the same species can produce fertile offspring. However, within certian species there is variation. Every species is given two latin name i.e. Homo Sapiens. This is the binomial naming system. Members of the same species tend to live in the same habitat. But, closely related species can be found in different places where conditions are different. This is due to adaptation and evolution. Species can inherit characteristics so we expect similar species to be closely related to a common ancestor. Species classification takes in evolutionary relationships as well as ecological relationships.

Not all organisms with similar characteristics are desended from common ancestor. They may have evolved to survive in the same enviroment, hence devolped similar structures. e.g Dolphins, Whales and sharks. They are similar because of their habitat.

• Artificial classification-based on observed characteristics e.g. beaks. -Is designed for a practical purpose, convenience and simplicity. E.g. Linnaeus included all worm-like organisms, ranging from simple nematodes to snakes.
• Natural classification-Tries to use natural relationships between organisms. Considers more evidence, including internal and external features. Most classifications today are natural and based on evolutionary relationships.
• DNA sequencing-helped with understanding classification. Organisms that are closely related. E.g. brown bears and polar bears have high degree of Dna sequence similarity.

Food chains show the transfer of energy from organism to organism. Energy from the sun flows through a food chain when green plants absorb sunlight for photosynthesis. Plants are producers because they produce biomass through photosynthesis (algae and plankton are producers too). Consumers are organisms which eat other organisms, every food chain relys on plants.

Trophic level-the position or stage that an organism occupies in a food chain, what it eats & what eats it.

Biomass and energy are lost at every trophic level. Materials and energy are lost during egestion. Energy is lost movement and respiration, especially in birds and mammals, through heat loss and waste (exrectian) hence doesn't go into making biomass.

Excretory products & uneaten plants can be used to create new food chains.Organisms which eat both plants and animals can be primary or secondary consumers e.g. Humans.

The length of a food chain depends on the effiency of energy transfer.

Green plant(producer)-->Rabbit(primary consumer)-->stoat(secondary consumer) --> Fox (tertiay consumer)

• A fraction of the sun's energy is captured by the producer.
• The rabbits respire, produce waste products. They pass on a tenth of the energy they get from grass (10%): 90% is lost.
• the stoats respire, produce waste products. They pass on a tenth of the energy they got from the rabbit (10%): 90% is lost.
• the fox gets the last tiny part of the energy left after all the others have had a share.
• Due to the little amount of energy passed on, there are rarely 4th or 5th degree consumers.

Energy efficiency=(energy converted to biomass/total energy ) X 100.

Food chains can join to make food webs. If an organism is removed from, or added to, a food web it can have a huge impact on the other organisms.  

The number of organisms at each stage in a food chain can be shown as a pyrimid of numbers.

The number of organisms decreases as you go up the pyramid i.e. a lot of grass feeds a few rabbits, which feed less stoats, which feeds one fox. Pyramids of numbers usually look in pyramid shape, but not always.

They don't take into acoount mass, so it can create an oddly shaped pyramid. For example if one lettuce feeds a few slugs, then the amount of lettuce will be smaller than the amount of slugs. This can also occur if trees are at the bottom.

A problem with creating pyramids of numbers is that an organism may belong to more than one trophic level.

Pyramids of biomass show the dry mass of living material at each stage in the chain. They will always be pyramid shaped because they take in mass of the organisms into account.

Difficulty with this is that for biomass you have to dry out and weigh the organisms. Which is difficult when organisms like trees are involved.

The efficency of energy transfer explains the shape of biomass pyramids. Biomass is lost through the seperate stages. A lot of biomass remains in the ground as the root system, the rabbits and stoats lose biomass through faeces and urine, the fox gets the remaining biomass.

In a stable community, the removal of materials is balanced by the return of materials. So materials are constantly being recycled:

• When animals and plants grow they take in elements from the soil which are incorporated into their bodies.
• When animals die and decay, these mineral elements are released and can be taken by other living organisms to allow them to grow.

Carbon & Nitrogen are recycled elements.

In waterlogged or acidic soils, the recycling takes longer. This is because the waterlogged soil lacks oxygen for decomposers and and acidic soil is not the best pH for decomposers.

Carbon Cycle:

• Carbon dioxide is removed from the atmosphere by green plants (for photosynthesis)
• Plants and animals respire, releasing carbon dioxide into atmosphere.
• Soil, bacteria and fungi (decomposers) feed on dead plants animals, causeing them to break down, decay and release carbon dioxide into the air. (the microorganisms respire as they feed, passing carbon compounds along the food chain) this decy process makes elements available again to living organisms.

Feeding passes carbon compounds along a food chain. The burning of fossil fuels (combustion) also releases carbon dioxide into air. Soil bacteria and fugi are decomposers. They live on dead animals and plants and then respire, releasing carbon dioxide into the air.

Nitorgen Cycle:

The air is made up of 78% nitrogen, it's a vital element used in the production of protiens. Which are needed for growth in plants and animals. A lot of nitrogen is stored in the air but animals and plants can't use it because it's so unreactive.

• Plants absorb nitrates from soil to make protien for growth.
• Animals eat plants and use the nitrogen to make animal protien. Like carbon, feeding passes nitrogen through the food chain.
• Dead animals and plants are broken down by decomposers, releasing nitrates back into the soil.

Carbon in the sea:

• Marine organism shells are made of carbonates. The shells drop to the bottom of the sea when the organism dies.
• The shells fossilise to become limestone rock.
• Volcanic eruptions heat limestone and release carbon dioxide into the atmosphere. Carbon dioxide is also released during weathering of limestone.
• Oceans absorbing carbon dioxide act as carbon sinks.

• Nitrogen-fixing bacteria- Convert atmospheric nitrogen into nitrates in soil. Some of these bacteria live in the soil while others live in root nodules with certain plants (legumes) e.g. Peas.
• Nitrifying bacteria- Convert ammonium compounds into nitrates in the soil.
• Denitrifying bacteria- Convert nitrates and ammonium compounds into atmospheric nitrogen.

The size and distribution of any populayion will change over time. It can be affected by how well the organismscompete for limited resources. Similar animals in the same habitat will be close competition.

• Animals- Compete for food, water, shelter and mates.
• Plants- Compete for light, water and minerals.
• The better adapted competitiors will get the best resources, so they can survive and produce offspring.
• The interdependance of organisms determine their distribution and abundance.

Within nature there is a delicate balance between the population of predator and prey. But, the prey will always outnumber the predators. There will be cyclical fluctuations in the numbers of each species because the numbers of predator and prey will regulate each other.

Normal amount of prey->Preadator increase due to lots of food->Prey decrease due to more being eaten->Predator decrease due to lack of food->begining.

There are two types of competition: Interspecific and intraspecific.

• Interspecific- where individuals or different species compete for the same resources in an ecosystem (e.g. food).
• Intraspecific- is where individuals from the same species are competing for the same resource. this is more specific as the organisms have the exact same needs.

Similar organisms in similar habits will have the same prey and nesting sites. They compete to occupy the same ecological niche (place and function). They will be in direct competion for the resources they need. E.g. red and grey squirrels.

Red squirrels are the native species to the UK. Grey squirrels were introduced from the USA. Forcing both species to compete for the same resources. This has lead to red squirrels being endangered.

Organisms that survive by living off other organisms are known as parasites. E.g. fleas or tape worms. The organism a parasite lives off is called the host organism.

Parasites can make the host organism ill, or even kill it.For example tape worm. The tapeworm gets into the human when they eat pork wich is infected with tapeworm larvae. The tapeworm absorbs food from the person's gut, making them extremely ill.

In mutualistic relationships, two organisms form a relationship from which both organisms benifit. For example, oxpecker birds live on buffalos' backs. The oxpecker gets a ready supply of food from the flies and ticks on a buffalo's skin. The buffalo benifits as the birds rid it of pests and warn it in advance, by hissing, if there are lions or other predators approaching. Organisms like the oxpecker are known as "Cleaner" species.

Adaptations are special features or behaviours that make an organism particularly well suited to its environment. As plants and animals become better adapted to their environment they become better able to compete for limited resources, which enables their population size and distribution to increase. If climate changes those with quick adaptation will survive.

Examples of adaptations to cold environments:

• being well insulated to reduce heat loss
• having small surface area to volume ration to prevent heat loss
• behavioural adaptations to help animals to survive cold temp. E.g hedgehogs hibernate.

Polar bears:

• small ears and large bulk reduce surface area to volume ratio to reduce heat loss
• large amount of insulating blubber beneath the skin.
• thick white fur for insulation and camouflage
• large feet to spread its weight on snow and ice
• fur on the soles of its paws give insulation and grip.
• powerful legs for running and swimming.

Penguins have a heat exchange blood flow to the colder regions. Warm blood entering the feet and flippers flows past cold blood leaving the feet, and arms it up. The warmed up blood re-enters the body and doesn't affect the penguin's core temperature.

Animals in hot environments do behaviours like: finding somewhere cool to stay; only going out at night and shedding fur. These all reduce heat gain. Behaviours like: taking a swim and panting, increase heat loss.

Cacti:

• Cope with lack of water by having long roots to reach water
• a thick waxy cuticle to reduce water loss
• having spines to reduce water loss and protect the water ,stored in the spongy layer, from predators.

Camels:

• body fat is stored in hump, which means lack of body insulation, keeps camel cool.
• drinks many litres of water in one go and stores extra water in blood
• can tolerate changes in body temperature, so rarely sweats
• hair-lined nostrils trap moisture and return it to the body.

Some organisms are biochemically adapted to extreme conditions. These organisms are called extremophiles.They have enzymes wich work at different optimum conditions. E.g some antarctic fish contain ant-freeze protiens wich prevent ice crystals forming in the tissue.

Some organisms are specialists so are only suited to certain habitats. Other organisms are generalists so they can live in a range of habitats, but can be easily out-competed by other organisms.

Natural selection - The theory that animals and plants that are better adapted to their environment are more likely to survive. It was first put forward by Charles Darwin. Evolution is the slow continual change of organisms over a very long period to become better adapted to their environment.