Sl Ecology And Evolution

Front 1

Define species, habitat, population, community, ecosystem and ecology

Back 1

Species: a group of organisms that can interbreed and produce fertile offspring
Habitat: the environment in which a species normally lives or the location of a living organism.
Population: a group of organisms of the same species who live in the same area at the same time.
Community: a group of populations living and interacting with each other in an area.
Ecosystem: a community and its abiotic environment.
Ecology: the study of relationships between living organisms and between organisms and their environment.

Front 2

Distinguish between autotroph and heterotroph

Distinguish between consumers, detritivores and saprotrophs

Back 2

Autotroph: an organism that synthesizes its organic molecules from simple inorganic substances.
Heterotroph: an organism that obtains organic molecules from other organisms.

Consumer: an organism that ingests other organic matter that is living or recently killed.
Detritivore: an organism that ingests non-living organic matter.
Saprotroph: an organism that lives on or in nonliving organic matter, secreting digestive enzymes into it and absorbing the products of digestion.

Front 3

Describe what is meant by a food web

Back 3

Food web: A series of interlinking food chains.

Front 4

Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms)

Back 4

Food chain: A linear feeding relation displaying the transfer of matter and energy from one organism to another in the form of food.

Phytoplankton -> Zooplankton -> Minnow -> Osprey
Periwinkle plant -> moth -> frog -> snake -> hawk
Clam -> starfish -> sea otter -> orcas

Front 5

Define trophic level

Back 5

Trophic level: The feeding position an organism occupies on a food chain.

Front 6

Deduce the trophic level of organisms in a food chain and a food web

Back 6

Producer (green plant) -> Primary consumer (herbivore) -> secondary consumer (carnivore)

Primary consumers are the species that eat the producers. Secondary consumers are the species that eat the primary consumers and tertiary consumers in turn eat the secondary consumers.

Front 7

Construct a food web of up to 10 organisms, using appropriate information

Back 7

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Front 8

State that light is the initial energy source for almost all communities

Back 8

Light is the initial energy source for almost all communities.

Front 9

Explain the energy flow in a food chain

Back 9

At each trophic level energy is lost. It may have not been consumed, not absorbed or lost through respiration. The energy left is what is available for the next trophic.









Efficiency as a percentage = (Energy remaining/Initial energy) x 100

Front 10

State that energy transformations are never 100% efficient

Back 10

Energy transformations are never 100% efficient, usually between 10% and 20%.

Front 11

Explain reasons for the shape of pyramids of energy

Back 11

A pyramid of energy shows the transfer of energy from one trophic level to the next in a community. They are always pyramidal in shape because energy is always lost between each trophic level.

Energy not consumed
Energy not absorbed
Energy lost through respiration




The red boxes represent the energy lost going from one trophic level to another.

Front 12

Explain that energy enters and leaves ecosystems, but nutrients must be recycled

Back 12

Energy enters an ecosystem as light energy trapped by photosynthesis. All this light energy is eventually converted to heat energy, this leaves the ecosystem and radiates into space. Nutrients are recycled through the food chain.

Front 13

State that saprotrophic bacteria and fungi (decomposers) recycle nutrients

Back 13

Saprotrophic bacteria and fungi (decomposers) recycle nutrients

Front 14

Analyse the changes in concentration of atmospheric carbon dioxide using historical record

Back 14

Since 1958, the concentration has been monitored continuously at Mauna Loa, Hawaii. There is an annual fluctuation, but the overall trend has been upwards, and the concentration is now more than 100ppm higher than in 1990. These changes are significant. There could be many causes. However, the most likely is the increased greenhouse effect.

Front 15

Explain the relationship between rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect

Back 15

The greenhouse effect is a natural phenomenon, and has helped to create a warm atmosphere that allows life on the planet. Greenhouse gases include carbon dioxide, methane, nitrogen oxides and water vapour. Carbon dioxide levels have been rising due to the increasing use of fossil fuels. This causes increased greenhouse gases in the upper atmosphere. More greenhouse gases cause a higher proportion of long-wave radiation to be reflected back. This is known as the enhanced greenhouse effect.

Front 16

Outline the precautionary principle

Back 16

The precautionary principle holds that, if the effects of a human-induced change would be very large, perhaps catastrophic, those responsible for the change must prove that it will not do harm before proceeding. This is the reverse of the normal situation, where those who are concerned about the change must prove that it will do harm in order to prevent such changes going ahead.

Front 17

Evaluate the precautionary principle as a justification for strong action in response to the threats posed by the enhanced greenhouse effect

Back 17

There are a number of points to consider:
- Does the economic harm at current outweigh how it could potentially harm?
- Is global warming too far into the future to worry about?
- Can we rely on future technologies to solve the problem later?
- Is it really happening? Arguments are on both sides of the fence.
- Is there enough data that we know how to act?
- Regardless of the answers to these questions, if we do nothing the result could be catastrophic to the biosphere and thus the precautionary principle should be followed.

Front 18

Outline the consequences of a global temperature rise on arctic ecosystems

Back 18

- If arctic soil starts to thaw, then decomposition of organic matter could release more CO2
-Loss of ice habitat
-Increase in sea levels
-Increased salinity of the ocean
-Expansion of the habitats available to temperate spcies
-Changes in distribution of prey
-Increased success of pest species and pathogens

Front 19

Outline how population size is affected by natality, immigration, mortality and emigration

Back 19

A population may increase in size due to natality (birth) and immigration from other populations

A population may decrease in size due to mortality (death) and emigration to other populations

Front 20

Draw and label a graph showing a sigmoid (S-shaped) population growth curve

Back 20

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Front 21

Explain the reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases

Back 21

Exponential growth phase: natality high, mortality low, few predators, less disease and abundant resources.
Transitional phase: competition for resources increasing, greater number of predators, disease, natality decreasing and mortality increasing.
Plateau phase: natality + immiagration = mortality + emigration (max environment can support)

Front 22

List three factors that set limits to population increase

Back 22

Competition for resources, predation, disease/parasites

Front 23

Define evolution

Back 23

Evolution: The cumulative change in the heritable characteristics of a population

Front 24

Outline the evidence for evolution provided by the fossil record

Back 24

- The fossil remains of extinct species provide evidence that species are continuously evolving
- Older rocks contain simpler organisms and species that are no longer living
- Younger rocks contain species that resemble those alive today

Front 25

Outline the evidence for evolution provided by selective breeding of domesticated animals

Back 25

- Humans select a particular feature; breeding from animals that possess it
- Offspring show an increase in the particular feature
- The changes of this artificial selection can be tracked over time
- The result is a species with more of the desired characteristic

Front 26

Outline the evidence for evolution provided by homologous structures

Back 26

- Homologous structures have the same origin, but now have different functions
- For example, the pentadactyl limb, which gives the origins of the human arm, horse hoof, bat wing and many more
- These structures are difficult to explain without evolution

Front 27

State that populations tend to produce more offspring than the environment can support

Back 27

Populations tend to produce more offspring than the environment can support

Front 28

Explain that the consequence of the potential overproduction of offspring is a struggle for survival

Back 28

Populations tend to produce more offspring than the environment can support. Therefore, there must be a struggle for survival, as the environment does not have the resources needed to support all of them

Front 29

State that the members of a species show variation

Back 29

Members of a species show variation.

Front 30

Explain how sexual reproduction promotes variation in a species

Back 30

Although mutation is the original source of new genes or alleles, sexual reproduction promotes variation by allowing the formation of new combinations.
- Meiosis allows a variety of genetically different gametes to be produced by the random alignment of bivalents and crossing over
- Fertilization between gametes is random

Front 31

Explain how natural selection leads to evolution

Back 31

Populations tend to produce more offspring than the environment can support. Therefore, there must be a struggle for survival, since there will not be enough resources to supply all of them. Individuals that show variations more adapted to the environment are more likely to survive. Those individuals with these favourable, heritable variations survive, and their reproductive success means they pass on these characteristics to their offspring. This leads to a change in the characteristics of a population.

Front 32

Explain two examples of evolution in response to environmental change

Back 32

Antibiotic resistance in bacteria: Mutation in the rapidly multiplying bacteria can lead to a resistant variety. Bacteria more resistant to the antibiotic being used are favoured, and therefore more likely to survive. Over time, these bacteria reproduce and the gene for antibiotic resistance increases in the population.

Peppered moths: They started out mostly light coloured. However, during the industrial revolution coal-burning factories blackened nearby trees and the air. The light coloured moth could easily be seen by birds and other predators. However, the dark moths survived more easily and the dark colouring increased in the population.

Front 33

Outline the binomial system of nomenclature

Back 33

Each organism has two Latin names, its genus and species. It is typed in italics, or underlined when handwritten. The genus starts with a capital letter; the species starts with a lower case.

Front 34

List the levels in the hierarchy of taxa using an example from the plantae kingdom for each level

Back 34

Kingdom: Plantae
Phylum: Angiospermaphyta
Class: Dicotyledonaea
Order: Ranales
Family: Ranunculacae
Genus: Ranunculus
Secies: Acris
Common name: Meadow buttercup

Front 35

List the levels in the hierarchy of taxa using an example from animal kingdom for each level

Back 35

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: Sapiens
Common name: Human