Ecology Flashcards
What problem is caused when fertilisers enter rivers and lakes?
Eutrophication
Give an advantage and disadvantage of intensive farming methods
Advantage - boosts food production
Disadvantage - destruction of habitats, pollution, reduction in diversity
What is intercropping?
The practice of growing two or more crops in the same field at the same time. This uses space efficiently, and makes maximum use of the soil nutrients.
Intercropping also encourages diversity
Explain how planting hedgerows helps to minimise negative effects of agriculture on ecosystems
Hedgerows increase the number of habitats available for colonisation and thus species diversity
Explain how planting trees helps to minimise the negative effects if agriculture on ecosystem
Trees act as wind shields and also prevent soil erosion
Explain how planting the legumes helps to minimise the negative effects of agriculture on ecosystems
Legumes naturally restore nitrates to the soil
Instead of chemical pesticides, what alternative method farmers can use to get rid of pests?
Biological control
List three different categories of pesticide
Herbicides, fungicides, and insecticides
Give two advantages of chemical control
It is often very effective at completely eradicating the pest species
It is relatively fast compared to biological control
Give three disadvantages of chemical control
It may be toxic to non-target organisms
It may be non-biodegradable and persist in the environment
It may bioaccumulate in living organisms
What is meant by biological control?
The use of a parasite or predator to control the number of pests (e.g. Aphids are controlled by the use of ladybirds)
Biological control also includes breeding pest-resistant crops
Give three advantages of biological control
It is very specific
Pests do not usually become resistant to biological control
It does not pollute the environment
Give three disadvantages of biological control
It is relatively slow compared to chemical control
Pests are never completely eliminated, so there is always some damage to crops
The control organism may become a pest in its own right
What is pollution?
A change in the abiotic or biotic characteristics of the environment as a result of human activities which introduce harmful substances into the atmosphere and water supplies
Name two gases that contribute to the production of acid rain
Sulphur dioxide and nitrogen oxides
Name two gases that contribute to the greenhouse effect
Carbon dioxide and methane
Explain how the greenhouse effects may lead to global warming
The ‘greenhouse gases’ prevent some of the sun’s radiation heat from leaving the atmosphere. As the concentration of these gases increases, more heat is trapped in the atmosphere, leading to an increase in the average temperature of the earth - global warming
Suggest one environmental consequence of global warming
Melting of the polar ice caps, leading to rising sea levels and flooding
What is eutrophication?
The decrease in biodiversity resulting from the pollution of a river or lake.
The pollutants stimulate the growth of algae in the water, which eventually die leading to an increase in the respiration of aerobic decomposers (e.g. bacteria)
Suggest two possible causes of eutrophication
Fertilisers and sewage entering rivers or lakes
Outline how eutrophication leads to reduced species diversity in a river or lake
The algal bloom caused by eutrophication and the subsequent increase in aerobic respiration by the the decomposing bacteria results in an increased biochemical oxygen demand and subsequent reduction in oxygen concentration in the water.
Consequently, many aquatic organisms, such as fish, die due to a lack of oxygen, reducing species diversity in the river or lake
What is succession?
The process by which plant communities gradually develop on bare land.
The end point of succession is the development of a stable climax community
What is primary succession?
Primary succession occurs on land where there is no soil and no living organisms, such as created by volcanic eruption
What is secondary succession?
Secondary succession occurs when most of the living organisms in an area have been destroyed but the soil and some living organisms remain.
E.g. Woodland that has been destroyed by fire
Describe how quadrats are used to investigate ecosystems
Quadrats are used to sample areas of plant cover and can be point or area quadrats of different sizes. They provide information about percentage cover, species richness and diversity
Describe how transects are used to investigate ecosystems
Transects are used to survey an area and are useful in investigating trends, such as the distribution of organisms on a rocky shore
They may be along a single line or in a belt of land
Define carrying capacity
Maximum population that can be maintained over a time in a particular habitat
Define intraspecific competition
Competition between individuals of the same species
Define interspecific competition
Competition between individuals of different species
What is meant by the term diversity?
A measure of the number of different species present in an ecosystem
Outline the distinguishing features of an ecosystem with low diversity
Low diversity is common in extreme ecosystems such as deserts, tundra and salt marshes.
In these areas, plant and animal populations are mainly affected by abiotic factors and the diversity index is low
Outline the distinguishing features of an ecosystem with high diversity
High diversity is common in ecosystems that are usually mature, natural (not created by human activity) and have environmental conditions that are not too hostile.
In these ecosystems, populations are mostly affected by biotic factors, and so the diversity index is high
What is meant by the term population?
A population is a group of individuals of the same species occupying a certain area
Distinguish between population size and population density
Population size refers to the total number of individuals present in a given area
Population density is a measure of the number of individual organisms per unit area
Explain what are density-dependant factors
Density-dependant factors are factors limiting the size of a population whose effects are proportional to the density of the population
These factors tend to be biotic, for example, food supply (for both predators and prey) and infectious disease
Explain what are density-Independant factors
Density-Independant factors are factors limiting the size of a population.
These factors tend to be abiotic, for example, temperature and water availability
What is a pyramid of biomass?
A pyramid of biomass shows the mass of organisms at each tropic level in a food chain
What are the two main factors that contribute to the destruction of natural habitats?
Expansion of human population
Over-exploitation of resources (e.g. Deforestation)
What are measures that have been put in place to promote habitat conservation in the UK?
National Parks
Sites of Specific Scientific Interest (SSSIs)
Environmentally Sensitive Areas (ESAs)
Wildlife Reserves
Name two environments in which species can be conserved outside their natural habitats
Zoos and botanical gardens
What is conservation?
The protection and maintainable of natural resources
List the key resources required for human life
Food water
Land
Other species
Minerals and other raw materials
Energy
Define tropisms
Growth movement in response to a stimulus e.g. Light
Define taxis
A type of response to directional stimulus seen in motile developmental stages of lower plants (e.g. moss)
Moving to/away from a stimulus
Define nastic movements
‘Rapid’ response - e.g. Flower closing when touched
Explain why plants need to respond to their environment in terms of the need to avoid predation and abiotic stress
Plants respond to external stimuli as well as biotic and abiotic components of the environment to help the plant avoid stress, being eaten, and survive long enough to reproduce.
These responses are coordinated by hormones
Explain how plant responses to environmental changes are co-ordinated by hormones, with reference to responding to changes in light direction
The presence of auxin promotes the active transport of hydrogen ions through the ATPase enzyme, into the cell wall.
This decreases the pH and allows optimum conditions for the wall loosening enzymes to work.
These enzymes break bonds within the cellulose, so the walls become less rigid and can expand as the cells take in water.
A shoot bends towards a light source because auxin in transported to the tip o the shoot to the cells in the shade, allowing the cells to take up more water and elongate.
Because the cells elongate more on the shaded side than the side in the light, the shoot bends towards the light source
Evaluate the experimental evidence for the role of auxins in the control of apical dominance
Apical dominance is when the growing apical bud at the tip of the shoot inhibits the growth of the lateral buds further down the shoot
Auxins are produced in the tip of the main shoot. They inhibit the growth of side shoots
When the tip of the main shoot is removed, or an auxin transport inhibitor is applied below the apex of the main shoot, the side shoots grow.
This shows that auxin is produced in the apex of the main shoot and transported to lateral buds to inhibit their growth.
When there are low concentrations of auxin in the side shoots, their growth is not inhibited, and so they can grow.
This is also shown where, as the plant grows taller, the lateral buds at the bottom of the plants start to grow larger - they are further away from the main shoot, so there is a lower concentration of auxin and their growth is less inhibited
Evaluate the experimental evidence for the role of gibberellin in the control of stem elongation
If genetically dwarf plants are treated with Gibberellic acid, the stems elongate considerably
Outline the role of hormones in leaf loss in deciduous plants
Cytokinins stop the leaves of deciduous trees senescing by making sure that the leaves act as a sink for phloem transport, so the leave is guaranteed a good supply of nutrients
If cytokinin production drops, the supply of nutrients dwindles and senescence begins
Senescence causes auxin production at the tip of the leaf to drop
This makes the cells in the abscission zone more sensitive to ethene
A drop in auxin concentration causes an increase in ethene production
This increases production of cellulase, which digests the walls of the cells in the abscission zone, eventually separating the petiole from the stem
Describe how plant hormones are used commercially
Synthetic auxins are used as growth stimulants when root cuttings are taken
A synthetic auxin is used as a selective weed killer
A form of abscisic acid what is not readily broken down by plants is used as an anti-transpirant as it closes stomata
What are plant growth substances?
Substances produced by the plant in response to stimuli
They move through the plant and bind to specific receptors on target cells
What are the five types of plant growth substance?
Auxins - associated with cell enlargement and differentiation
Gibberellins - also associated with cell enlargement and
differentiation
Cytokinins - associated with cell division
Abscisic acid - usually associated with dormancy, as with buds
Ethene - often associated with ageing (senescence)
