7.2 organisation of an ecosystem

define producer

makes its own food e.g plants

define consumer

cannot make its own food so has to eat another organism e.g all animals

define herbivore

only eats plants e.g sheep

define carnivore

eats other animals e.g lions

define omnivore

eats both plants and animals e.g humans

define decomposer

breaks down dead organic material e.g fungi

what is a food chain?

a diagram showing how energy passes from organism to organism, or the feeding relationships within a community

what do food chains usually look like?

producer (plant) →herbivore (primary (1st) consumer)→carnivore (secondary (2nd) consumer)→top carnivore (tertiary (3rd) consumer)

what do the arrows in a food chain represent?

transfer of energy and the movement of biomass

what happens to the most of the energy as it passes along a food chain?

most of the energy is lost to the surroundings

what are predator-prey cycles?

The cyclical increase and decrease of predator and prey populations over time

If the prey species rapidly multiplies, soon afterwards, the number of predators increases - until the predators eventually eat so many prey that the prey population falls again

what are the advantages and disadvantages of being a primary consumer?

primary consumers eat plants or algae

-the cellulose in cell walls is difficult to digest

-herbivores have to break down the cell wall to get to the contents

-however they don’t have to catch their prey first

what are the advantages and disadvantages of being a secondary/tertiary consumers?

-their food (prey) is high in protein and fat and relatively easy to digest

-but animals move about so they have to catch them

what are the limitations of food chains?

they suggest that each type of consumer eats one type of organism

what factors affect the distribution of organisms?

-new predators

-new pathogens

-out competition

-moisture levels

-soil pH content

-soil mineral content

-temperature

-availability of food

define abundance

how many individuals of a species there are

define distribution

where the individuals of a species are located

what are the different ways of using a quadrat?

-count all the individuals of a species found inside the quadrat

-decide if each species is abundant, common or rare

-estimate the percentage cover - if every square was filled it would be 100%

how to set up a line transect?

-stretch a tape between two points

-sample the organisms along that line at regular intervals using a quadrat - this shows how the distribution of organisms changes along the line

-can also measure some physical factors, such as light levels and soil pH

when should a line transect be used?

if there is a gradual change in the physical conditions across a habitat

define organic compounds

are produced by living things and contain carbon (and hydrogen)

examples include: glucose and other sugars, starch, proteins, fats, DNA

define carbon sink

absorbs more carbon dioxide than it releases

e.g oceans, forests

define carbon source

releases more carbon dioxide than it absorbs

e.g anything that burns fossil fuels, volcanoes, animals

in the carbon cycle, which process removes carbon dioxide from the atmosphere?

photosynthesis

in the carbon cycle, which processes release carbon dioxide into the atmosphere?

-respiration

-decomposition

-combustion (burning fossil fuels)

what is the name of the process by which dead plants and organisms are broken down?

decomposition

define precipitation

rain, hail, snow, sleet etc

define evaporation

liquid water turns into water vapour

define percolation

water drains into the soil

define condensation

water vapour turning back into liquid

define transpiration

evaporation of water from inside leaves to release water vapour into the atmosphere through the stomata

what are the steps of the water cycle?

-water from lakes, rivers, oceans, and the soil, evaporates into water vapour and rises into the atmosphere

-water can also evaporate from plants through transpiration

-as the water vapour accumulates, it can condense to form clouds

-later the water will fall as rain (precipitation)

-the water will then seep into the soil, flow into rivers or lakes, and be taken up by plants

-the whole cycle then repeats

what is the importance of water to living organisms?

-it is a reactant (used in photosynthesis)

-transport systems based on it (transfer medium)

-it allows chemical reactions to take place

-water evaporates to keep organisms cool and therefore help them to regulate their temperature

how is the water cycle affected by humans?

-deforestation - reduces transpiration

-building on land - reduced percolation and causes more surface run off, leading to flooding

-global warming - increases temperature causing more evaporation and rainfall