Topic 5 - Ecology and Evolution Flashcards
5.1.1 Define Species
A group of organisms that can interbreed and produce fertile, viable offspring
5.1.1 Define Habitat
The environment in which a species normally lives of the location of a living organism
5.1.1 Define Population
A group organisms of the same species who live in the same area at the same time
5.1.1 Define Community
A group of populations living and interacting with each other in an area
5.1.1 Define Ecosystem
A community and its abiotic envrionment
5.1.1 Define Ecology
The study of relationships between living organisms and between organisms and their environment
5.1.2 Distinguish between autotroph and heterotroph
Autotroph:
An organism that synthesises its organic molecules from simple inorgance substances - autotrophs are producers
Heterotroph:
An organism that obtains organic molecules from other organisms - heterotrophs are consumers
5.1.3 Define ‘consumer’
An organism that ingests other organic matter that is living or recently killed
5.1.3 Define Detritivore
An organism that ingests non-living organic matter
5.1.3 Define Saprotroph
An organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion
5.1.4 Decribe what is meant by a food chain
A food chain shows the linear feeding relationships between species in a community,
The arrows represent the transder of energy and matter as one organism is eaten by another.
The first organism in the sequence is the producer, followed by consumers
5.1.5 Describe what is meant by a food web
A food web is a diagram that shows how food chains are linked together into more complex feeding relationships within a community.
There can be more than one producer in a food web, and consumers can occupy multiple positions
5.1.6 Define Trophic Level
An organism’s trophic level refers to the position it occupies in a food chain.
Producers always occupy the first trophic level, while saprotrophs would generally occupy the ultimate trophic level of a given food chain or food web/
Level 1 : Producer
Level 2: Primary Consumer
Level 3: Secondary Consumer
Level 4: Tertiary Consumer
5.1.7 How can you determine the trophic level of organisms in food webs and chains?
Counting the number of feeding relationships preceding it and adding one
Trophic Level: Number of arrows (in sequence) before organism +1
In food webs, a single organism may occupy multiple trophic levels
5.1.9 What is the initial source of energy for most communities?
Light.
All green plants, and some bacteria are photo-autotrophic - they use light as a source of energy for synthesising organic molecules
5.1.10 Explain the energy flow in a food chain
Energy enters most communities as light, where it is absorbed by autotrophs, and converted into chemical energy via photosynthesis.
Energy then gets passed to the primary consumer (herbivore) when they eat the plan, and then gets passed to successive consumers (carnivores) as they are eaten in turn
Only ~10% of energy is passed from one trophic level to the next, the rest is lost.
Because ~90% of energy is lost between trophic levels, the number of trophic levels are limited as energy flow is reduced at higher levels
5.1.11 Are energy transformations every 100& efficient?
Typically energy transformations in living thigns are ~10% efficient, with about 90% of the energy lost between trophic levels. This energy may be lost as heat, be used up during cellular respiration, be excreted in faeces or remain unconsumed as the uneaten part of the food.
5.1.12 Explain the reason for the shape of pyramids of energy
A pyramid of energy is a graphical representation of the amount of energy of each trophic level in a food chain
They are expressed in units of energy per area per time (e.g. kJ m2 year -1).
Pyramids of energy will never appear inverted as some of the energy stored in one source is always lost when transferred to the next source
This is an application of the second law of thermodynamics
Each level of the pyramid of energy should be approximately one tenth the size of the level preceding it, as energy transformations are ~10% efficient
5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled
The movement of energy and matter through ecosystems are related because both occur by the transfer of substances through feeding relationships.
However, energy cannot be recycled and an ecosystem must be powered by a continuous influx of new energy from an external source
Nutrients refer to material required by an organism, and are constantly being recycled within an ecosystem as food
The autotrophic activities of producers produce organic materials from inorganic sources, which are then fed on by the consumers.
When heterotrophic organisms die, these inorganic nutrients are returned to the soil to be reused by the plants
Thus energy flows through ecosystems, while nutrients cycle within them
5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients
Certain bacteria and fungi ensure a continual supply of raw materials for the producers, by freeing inorganic materials from the dead bodies and waste products of organisms.
Thus saprotrophic bacteria and fungi play a vital role in recycling nutrients within an ecosystem.
5.2.1 What are the four main ‘pools’ of carbon in our environment?
Atmosphere, Biosphere, Sediments, Ocean
5.2.1 Name the processes by which carbon can be cycled between the carbon ‘pools’
PHOTOSYNTHESIS
Atmospheric carbon dioxide is removed and fixed as organic compounds
FEEDING
In which organic carbon is moved from one trophic level to the next in a food chain
RESPIRATION
All organisms metabolise organic compounds for energy, releasing carbon dioxide as a by-product
FOSSILIZATION
In which carbon from partially decomposed dead organisms becomes trapped in sediment as coal, oil and gas
COMBUSTION
During the burning of fossil fuels and biomass. In oceans, carbon can be reversibly trapped and stored as limestone.
5.2.2 Analyse the changes in concentration of atmospheric carbon dioxide using historical records
RECENT
- Atmospheric carbon dioxide concentrations have been measured across a number of locations globally, the data shows there is an annual cycle in carbon dioxide concentrations, which may be as a result of seasonal factors, but when data from two hemispheres is incoperated it suggests that atmospheric carbon dioxide levels have steadily risen over the last 30 years.
LONG TERM
- Carbon dioxide concentration changed over a long period of time, which would have been due to a variety of sources, including analysing the gases trapped in ice
- Data taken from Antartica shows that fluctuating cycles of carbon dioxide concentrations over thousands of years appear to correlate with global warm ages and ice ages
- It is compelling to note that carbon dioxide levels appear to be currently higher than at any time in the last 400,000 years
5.2.3 Explain the relationship between the rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect
The greenhouse effect is a natural process, whereby the earth’s atmosphere behaves like a greenhouse to create moderate temperatures to which life on earth has adapted.
The incoming radiation from the sun is short-wave ultraviolet and visible radiation. Some of this radiation is reflected by the earth’s surface back into space as long-wave infrared radiation.
Greenhouse gases absorb this infrared radiation and re-reflect it back to the earth as heat, resulting in increased temperatures (greenhouse effect).
The enhanced greenhouse effect refers to the suggested link between the increase in greenhouse gas emissions by man and changed in global temperatures and climate conditions.
The main greenhouse gases are water vapour, carbon dioxide, methane and oxides of nitrogen. Whilst these gases occur naturally, man is increasing greenhouse gas emissions by a number of processes, including deforestation, industrialization, increased farming/agriculture. With increases in greenhouse gas emissions, it is thought that the atmospheric temperature may increase and threaten the viability of certain ecosystems, although this link is still being debated.
