Topic 4: Ecology Flashcards
State one greenhouse gas. [1]
Carbon dioxide/methane/nitrogen oxides/water vapour/ozone/CFCs
Explain how radiation of different wavelengths is involved in the greenhouse effect. [2]
- incoming short-wave radiation (UV) passes through the earth’s atmosphere
- converted to long-wave radiation (infrared)
- atmosphere traps infrared
Outline two consequences of a global temperature rise on arctic ecosystems. [2]
- loss of ice habitat
- risk in sea levels
- changes in the distribution of prey species, affecting higher trophic levels
- increased rates of decomposition
Outline one effect of a temperature rise on plants. [1]
- rate of photosynthesis increases
- rate of transpiration increases
Define habitat, population, community and ecosystem. [4]
Habitat: the environment in which a species normally lives
Population: a group of organisms of the same species living in an area at one time
Community: multiple populations of different species living and interacting in the same area
Ecosystem: a community and its interactions with abiotic parts of its environment
Outline how energy flows through an ecosystem. [6]
- producers convert light energy into chemical energy (photosynthesis)
- such as organic compounds
- energy moves up trophic levels
- 10% of energy passed along the food chain
- energy lost in the form of heat
- lost by respiration
- lost as not digested/in faeces
- lost through death of organisms
- passed to decomposers
- energy not recycled
Describe what is meant by a food chain and a food web. [6]
Food Chain
- shows the transfer of nutrients/energy in an ecosystem
- between different trophic levels
- starting with a producer;
- followed by at least two levels of consumers
Food Web
- interaction of multiple food chains
- using (multiple) producers as a source;
- transferring nutrients/energy to consumers from different food chains;
- the same consumer could be at different trophic levels in a food web
Explain the relationship between rises in the concentration of atmospheric gases and the enhanced greenhouse effect. [8]
- water vapour;
- carbon dioxide;
- methane;
- oxides of nitrogen;
- all (of these gases) occur naturally;
- human activity has increased the normal level of greenhouse gases;
- incoming short-wave radiation (UV) from the Sun;
- is re-radiated as long-wave radiation (infrared);
- (mainly) in the form of heat;
- captured by greenhouse gases;
- increases the atmospheric/ocean temperature;
- at a higher rate than normal;
- threatens ecosystems/climatic patterns/ocean patterns;
Explain the processes by which energy enters and flows through ecosystems. [8]
- light energy (from Sun) initial energy source
- producers convert light energy to chemical energy
- produce organic compounds (sugars/carbohydrates)
- used for energy/growth/storage
- energy passes as food along trophic levels
- respiration releases energy as ATP from food
- energy lost as heat
- 10% energy passed to the next trophic level
- energy lost in undigested food/faeces
- passed to decomposers (remove energy from wastes)
- energy not recycled
Producers extract phosphates and nitrates from soil. Outline how these ions are used in the synthesis of organic molecules. [3]
- by photosynthesis / using energy from light
- attached to carbon compounds
- phosphates used to make phospholipids/nucleotides/nucleic acids/DNA/RNA/ATP
- nitrates are used to make amino acids/proteins/nucleotides/nucleic acids/DNA/RNA/ATP
Predict how global warming may threaten the survival of such an ocean bird. [1]
- global warming causes rising ocean levels, destroying breeding sites / drown baby birds
- populations cannot find new colony sites
- warming seas affect the food supply
Outline the energy flow through this food web. [3]
- light energy from the Sun is converted into chemical energy by autotrophs
- detritivores/saprotrophs decay plant material
- consumers release energy from carbon compounds by cell respiration, energy is lost as heat
- energy used for metabolism
- energy transferred between trophic levels
- 90% of energy lost between trophic levels
Describe what is meant by a food chain. [2]
- food chain shows feeding/trophic relationships
- shows which organisms eats which organism
- shows flow of energy from autotroph to top consumer through trophic levels
State one reason that the population of mountain lions is smaller than the populations of other animals in the food web. [1]
mountain lions are at the highest trophic level, receive the least energy as energy is lost between trophic levels
Aquatic and other environments are being affected by a global rise in temperature. Outline the consequences of this on arctic ecosystems. [6]
- loss of ice habitats
- raises sea levels
- decrease in size of populations
- arctic species move/adapt
- change in the distribution of species
- affects food webs/chains
- increased rates of decomposition of detritus
- increased success of pest species including pathogens
Distinguish between autotrophs and heterotrophs. [2]
autotrophs
- make their own food
- use inorganic molecules
heterotrophs
- obtain food from other organisms
- require complex organic molecules
Define saprotroph. [1]
an organism that feeds on dead organic matter and undergoes external digestion by secreting digestive enzymes on it
Ecologists sometimes display data from an ecosystem using a diagram called a pyramid of energy. Describe what is shown in pyramids of energy. [6]
- flow of energy from one trophic level to the next
- unit: kJ m^–2 yr^–1
- bar width is proportional to the energy stored in that trophic level
- first level: producers
- second level: primary consumers
- third level: secondary consumers
- only 10% of energy passed to the next trophic level
- bar width decreases proportionally going up trophic levels
- pyramid shows the limit to the length of food chains
Distinguish between the movement of energy and nutrients in an ecosystem. [2]
- energy enters and leaves ecosystems, constant source required
- nutrients cycled between biotic and abiotic environments
Explain how the flow of energy in the food web differs from the movement of nutrients. [2]
energy
- energy enters and leaves, no recycled and requires a constant source
- enters as light, lost as heat
nutrients
- recycled
- by saprotrophs, returned to environment and reused
Discuss reasons why the levels of a pyramid of energy differ in size. [2]
- shows energy lost from base to top, 90% of energy lost at each trophic level
- energy is released through cell respiration/heat/metabolism/movement
- not all tissues are eaten (undigested/excretion/death)
Outline the causes and consequences of the enhanced greenhouse effect. [5]
causes
- burning of fossil fuels releases CO2
- deforestation reduces CO2 uptake
- methane emitted from cattle
- causes global warming
consequences
- rising sea levels / melting ice caps
- extreme weather events
- changes in species distributions
- increased success in pest species including pathogens
Outline the precautionary principle. [2]
- some human-induced changes can be large/catastrophic
- those responsible for the change must prove it will cause no harm before proceeding
- e.g. companies must immediately reduce the emission of greenhouse gases despite proof of human impact on global warming is still debated
Define the terms species, population and community. [3]
Species: group of organisms that can interbreed to produce fertile offspring
Population: group of organisms of the same species living in the same area at the same time
Community: group of populations living and interacting with each other in the same area
Describe the relationship between the rise in the concentration of atmospheric carbon dioxide and the enhanced greenhouse effect. [5]
- CO2 is a greenhouse gas
- increase in CO2 enhances greenhouse effect
- greenhouse effect is a natural phenomenon but not its increase
- Earth receives short-wave radiation from the Sun
- re-radiated from the Sun as long-wave radiation
- greenhouse gas traps infrared
- CO2 concentration correlated positively with rising global temperatures
Describe the process of peat formation. [4]
- formed from dead plant material
- formed in waterlogged sites
- bacteria/fungi/saprotrophs inhibited
- organic matter not fully decomposed
- acidic conditions
- anaerobic conditions
- slow process/takes a long time
Describe how populations in communities rely on each other for supplies of energy. [7]
- autotrophs provide energy for consumers
- autotrophs convert light energy to chemical energy via photosynthesis
- energy flows along food chain/web
- heterotrophs rely on foods from other organisms
- consumers ingest food internally
- primary consumers feed on autotrophs
- secondary consumers feed on primary consumers
- detritivores ingest dead organic matter internally
- saprotrophs feed on dead organic matter externally by releasing digestive enzymes
- energy not recycled, lost as heat between trophic levels
Describe processes in the carbon cycle that produce or use carbon dioxide. [7]
- photosynthesis uses CO2
- autotrophs fix CO2 into organic compounds
- cell respiration releases CO2
- organic compounds broken down to release CO2
- CO2 released from aerobic and anaerobic respiration
- CO2 released from decomposers from dead organic matter
- partially decomposed organic matter leads to formation of peat
- CO2 released in combustion of fossil fuels
- CO2 dissolves in aquatic ecosystems
- reef-building corals use calcium carbonate to build shells/exoskeletons
- precipitation of calcium carbonate forms limestone
