OCR Gateway B Module B2: Understanding Our Environment

Different groups for classification:

There are 5 kingdoms, sorted by the following in this order:
Kingdom, phylum, class, order, family, genus, species
Arthropod groups: insects (6 legs), arachnids (8 legs), crustaceans (10-14 legs), myriapods (20+ legs)

Artificial: Based on 1-2 characteristics, e.g., birds that live by the sea: seabirds
Natural: Based on evolutionary relationships

To aid classification, the bases in DNA can be studied, this has caused organisms to be reclassified in recent years
Species can interbreed for fertile offspring
All organisms are named in a binomial system: two parts to the name, genus and species
Problems with the classification system:
- Some organisms (like Archaeopteryx) have two features with conflicting groups
- Bacteria reproduce asexually, so the 'fertile offspring' idea doesn't work
- Hybrids (eg mules) are infertile
- Closely related organisms may have different features if in different habitats
- Dolphins and fish live in the same habitat (ecologically related), but are classified differently; dolphins are mammals
- Dolphins and bats are both mammals, but have evolved very differently

Pyramids of biomass use the dry mass, organisms must be dead for this process. If producers are large or there are parasites involved, this will look very different to a pyramid of numbers
These are constructed with horizontal bars, each representing the number/mass of each trophic level and must be labelled with the organism

Some energy is used for growth, but most is lost through: heat lost by respiration, egestion, evaporation, reflection, energy loss by movement
This lost energy is therefore not passed on to the organism that consumes it
Energy transfer efficiency (%) = (energy used for growth ÷ total energy input) x 100

Carbon dioxide is released into the air by respiration, burning fossil fuels and decomposers
Oceans absorb carbon dioxide. It is also locked away in marine organisms' carbonate shells, which turns into limestone. It is returned to the air through volcanic eruptions or weathering

The air contains 78% nitrogen, an unreactive gas
Plants take in nitrates, which are used to make protein (for growth). Nitrogen gas cannot be used directly from the air because it is too unreactive for the process
Nitrogen compounds are passed on through the food chain
Nitrogen compounds in dead organisms are broken down by decomposers and returned to the soil
Decomposers convert proteins and urea to ammonia
Nitrifying bacteria convert nitrates to nitrogen
Nitrogen-fixing bacteria live on root nodules or in the soil. They fix nitrogen gas, which also happens through lightning. This process is: Nitrogen -> ammonium (NH₄⁺)
Decomposers need oxygen and a suitable pH, acidic conditions will slow decay

Similar animals in the same habitat compete for resources, those of the same species compete for mates
Interspecific competition is competition between organisms of different species
Intraspecific competition is competition between organisms of the same species
Numbers of predators and prey in a habitat fluctuates and shows cyclical ups and downs in numbers
- Predator numbers peak after the peaks of prey

Parasites feed on their host, this is known as dependance
However, in many cases both organisms benefit from the relationship, mutualism. Examples include insects transferring pollen and cleaner fish eating parasites from larger fish. In pea plants, nitrogen-fixing bacteria on the roots get sugars in return for converting nitrogen

Penguins have a counter-current heat exchange: cold blood from the flippers is warmed by warm bloog to prevent cold from entering the body
Some animals migrate to warmer areas, and some hibernate
Many animals have thick fur for insulation
Some have antifreeze proteins, such as penguin eggs

Camels have anatomical adaptations, which increase heat loss by having no hair on the underside of the body, cooling the camels down
Some organisms seek shade to cool down
Extremeophiles survive in hot conditions, like enzymes that don't denature under 100 degrees C
Polar bears are specialists, they would struggle to live elsewhere
Generalists live in many habitats, such as rats
However, generalists would lose to specialists in certain habitats
Water loss must also be reduced, for example cacti only have spines and can store water in the stem, camels have very concentrated urine

Lamack originally had the original idea of acquired characteristics, but this was discredited as there was no genetic basis

There is variation with all species, this causes the weaker to not survive, and these characteristics are passed on
We now know that genes are passed on, although Darwin didn't know this
The result of natural selection may create new species
If different groups of organisms cannot mate for a ong time, eg geographical or behavioral isolation, new species are created
Some bacteria have evolved to become resistant to antibiotics

The human population is growing exponentially, because the birth rate is higher than the death rate

Indicator species can be used to measure pollution levels in an area:
- Mayfly larva only live in clean water
- Water lice, bloodworms and mussels live in polluted water
- Lichen live on trees and rocks where the air is clean, so they are not found in most cities

Organisms become endangered/extinct due to climate change, habitat destruction, hunting, pollution and competition
Conservation proptects our food supply and food chains, tourism and study of nature. This can be done with seed banks, education, legal protection, artificial ecosystems and captive breeding programmes
Organisms need genetic variation to survive
Whales are important for the tourist trade, but they are hunted for food. Whales are not yet completely understood in their communication, migration patterns and survival at extreme depths
Sustainable development can be used to control levels, with tree planting and fishing quotas, for example