B2 - Understanding our environment

HideShow resource information


Kingdom, Phylum, Class, Order, Family, Genus and Species 

Or King Phylum Can Order Family Genocide Special

Atificial system is based to visisble characterisitics and similarities.

Natural sytem is based on thier evolutionary history and common ancestors.

A species is a group of animals that can interbreed and produce fertile offspring.

The Binomial System : Genus species eg. Homo sapiens.

The 'fetile offspring' way of catagorising specices has it's flaws. A mule is a hybrid but it can interbreed to produce fertile offspring so technically it's not a species. Also bacteria reproduces asexualy so it can't technicallly be a species. 

1 of 9

Energy Flow

Pyramids of Numbers Vs Pyramids of Biomass

The pyramids of biomass show the dry mass of living materialat each stage of the food chain. They tend to assume a phyramidal shape. 

As energy is passed from one trophic level to the next it is used on processes like heat from repsiration, egestion and excrection. Each trophic level 'looses' up to 90% of it's energy.

The efficency of energy transfer can be calculated between trophic levels:

energy used for growth/energy input = %efficency 

2 of 9

Carbon Cycle

The carbon cycle - because all living matter is primarily made of carbon the world needs this carbon to circulate so that more organic matter can be made. 

CO2 is removed from the atomsphere by photosynthesis.

Plants get eaten.

CO2 is released from animals by respiration, decomposition and from the earth by the burning of fossil fuels.

COis also absorbed by the oceans to create a 'carbon sink' and marine organsims make shells of carbonate, which becomes limestone rock and then the rock's CO2 is released thorugh the weathering of the rock or volcanic eruptions

3 of 9

Nitrogen Cycle

Plants absorb Nitrates through their roots from the soil to make proteins for growth.

Feeding passes the Ni along the web.

Then the Ni passes back into the soil when the plants and animals die.

A number of microrganisms are resonsible for the recylcing of nitrogen. First the soil bacteria and fungi break down the protein and urea into ammonia. Then Nitifying bacteria converts the ammonia to nitrates. The Nitrogen can also be fixed by Nitrogen Fixing bacteria in Root Nodules or by lightning strike. These methods directly convert Atmsopheric Ni into Nitrates for the plant.

However Atmospheric Ni levels must stay at around the same levels so Denitrifying bacteria convert some of the Nitrates back to Atmosheric Ni.

Decomposers need oxygen and a suitable pH:

-Decay is slower in acidic donditions

-Decay is slower in water-logged soil as there is less O2

4 of 9


An ecological niche describes the habitat that an organism lives in but alos it's role in that habitat.

Competition can be interspecific (between organisms of the same species) or intraspecific (between organisms of a different species).

Predator and prey numbers show cyclical changes. As when there are lots of predators the prey munbers fall, but once the prey numbers fall the predators don't have enough food then their numbers fall then becasue their numbers fall the prey numbers increase and due to the abundance in food the oredator numbers increase again. Remember : the predator peaks occur soon after the prey peaks, becasue reporduction take some time.

Parasites feed on a host and cause them harm.

Sometimes both organism benefit and this is called mutualism eg. bees and pollination of flowers

An excellent example of mutualism is the nitrogen-fixing bacteria in the roots of pea plant (which are a type of legume) which turn Ni into Ni containing chemicals that the pea can absorb and in returen the pea gives the bacteria some sugar from photosnthesis.

5 of 9


Penguins have a counter current heat system to help them save heat by making the warm blood entering the flippers warm the cool blood leaving them.

Large surface area to volume ratio means that the animals can loose heat quickly.

Small surface area to volume ratio means that the animal looses heat slowly.

Adaptations can be behavioral like panting or sweating.

-Camels can survive with little water becasue they have very concentrated urine.

Organisms that can survive in hot conditions are called extromophiles . Some bacteria that can live in hot springshave nezymes that do not denature at temperatures as high as 100C.

A specialist is an organism that is very well adapted for a specific habitat and would struggle to live elsewhere. A generealist is an organism that can live in several habitats.

6 of 9

Natural Selection

Natural Selection:

-Mutations causes genetic variation

-Too many young are born and there is competition for resources

-Only the best adapted survive (survival of the fittest)

-The survivers pass on their successful adaptations to the next generation in their genes.

Over time natural slection may produce a different species but only if: isloation of different groups occurs so they cannot mate for a long time. Geographic isolation or behavioral isolation. Eg. bacteria developing imunity to antibiotics / peppered moths thriving in polluted areas.

Before Darwin Jean Baptiste Lamarck had his theory of aquired characteristics said that the giraffe grew it's neck long because it needed too. Disproved.

People thought Darwin couldn't back up his theory and it clashed with religious views. 

7 of 9

Population & Pollution

-COfrom buring fossil fuels.

-CFCs, from aerosols, destroy the ozone layer.

-Sulfur dioxide, from burning fossil fuels, which causes acid rain.

The human population of the earth is exponantially growing. The population in developing countries is rising fastest however the developed countries have musch higher induvigual Carbon footprints. A carbon footprint is the total of greenhouse gas given off by a person within a cartain time.

Pollution in water and air can be measured using direct methods or indicator species. An example of a direct method could be oxygen probes attched to computers or chemicals indicators. 

In water : Freshwater shrimp = clean. Mayfly lava = clean. Water louse = dirty. Bloodworm = dirty. In air : Litchen = clean. Black spot Fugus on Roses = Clean.  

8 of 9


Conservation is important because we need to protect our food supply; prevent damage to food chains; protect plants that could be medicinal; procting organisms and habitats people would enjoy to visit or study.

Whales are very important to us as humans. Their body are used as resources and they are important to the tourist industry. Some poor whales are placed in captivity for captive breeding programmes

It super hard to police whaling and some morally deprived countries want to lift the ban. Some scientistst think that some whales should be killed for research, however we need some alive to study the migration patterns and whale song.

Sustainable development is the term for using your environment but leaving enough for the future and preventing damage.

9 of 9




this is B1 not B2

Similar Biology resources:

See all Biology resources »See all B2 resources »