B4 Flashcards
explain the role of microorganisms in the cycling of materials in an ecosystem
help return minerals and nutrients back to the environment so that the materials can then be used by other organisms. As the bacteria and fungi decompose dead matter, they also respire and so release carbon dioxide to the environment, contributing to the carbon cycle
Explain the stages and importance of the carbon cycle
Stages:
1. Carbon enters atmosphere as CO2 from respiration and combustion
2. Producers absorb CO2 by diffusion in photosynthesis to make carbohydrates
3. Animals feed on plants, passing carbon compounds along the food chain. Most carbon consumed is exhales as CO2 during respiration
4. When animals/plants die, they are eaten by decomposers and carbon is returned to the atmosphere as CO2. If decomposition is blocked, the plant/animal material may then be available as fossil fuel for future combustion
Importance:
- carbon is a component of all organic molecules, many of which are essential for life on earth, such as glucose
-key process which allows the movement of carbon between global reservoirs including the atmosphere, biomass, ocean and soil
- the balance of carbon between these reservoirs is fundamental due to the role that carbon plays in sustaining life
- so if the balance is disrupted, organisms will suffer
- global warming is an large scale example of the effect which may be seen if the global carbon balance is disrupted
Explain the stages and importance of the water cycle
Stages:
Evaporation: the Sun heats Earth’s surface and ocean water is turned from a liquid into water vapour, forming warm, moist air
Transpiration: loss of water vapour from plants directly to the atmosphere
Condensation: as the moist air from evaporation and transpiration rises, it cools, so water vapour condenses back into liquid water droplets producing clouds
Precipitation: as water droplets in clouds get heavier, they fall as rain, snow or hail
Percolation: water trickles through gaps in soils and rocks, and the remaining water undergoes ‘surface runoff’
Importance:
-all living organisms need to drink/absorb water to survive
-water determines physical characteristics of many habitats necessary for certain organisms to survive
-the cycle moves water and nutrients through the atmosphere, soil, rivers, lakes and oceans, so it brings fresh water to every living thing in the world
-the nutrients carried in the water are vital to replenish those that have been used within a habitat
Stages and importance of the nitrogen cycle
Explain the effect of factors such as temperature, water content, and oxygen availability on rate of decomposition
Temperatures:
-at high temperatures, the enzymes used by microorganisms are denatured, which prevents decomposition and results in the death of microorganism
-at low temperatures, the rate of decomposition is slow, as rate of enzyme-controlled reactions is reduced. Rate of microorganism replication also slows
Moist environment:
-if not enough water is available, reactions within decomposers will slow/be prevented, which reduces rare of decomposition
Oxygen availability:
-oxygen is needed for decomposers to respire
-therefore a lack of oxygen = less respiration = less chance of survival = lower rate of decomposition
Describe different levels of organisation in an ecosystem
-begins with a producer, like a green plant/algae. Producers make glucose
-producers are eaten by primary consumers, which are eaten by secondary consumers, etc
Food chains do not generally continue past tertiary consumers
The typical population cycle in a stable community:
-if the population of a prey increases, the predator population also increases
-this results in the number of prey decreasing, as more would be consumed by the predators
-when there isn’t enough prey to feed the predators, the population of predators decreases, so the population of prey can increase again
Explain how some biotic and abiotic factors can affect communities
Abiotic factors:
Temperature:
-higher temperature = more enzyme-controlled reactions = faster metabolism = faster growth of plants
-this is also the case for cold-blooded animals, which rely on the Sun for warmth
-warm-blooded animals are less affected by the external environment
Light intensity:
-light is required for photosynthesis
-more light availability = more successful plant
-plants evolve to grow successfully in different light intensities, e.g. plants in low light levels tend to have larger leaves, as more chlorophyll = more photosynthesis
Moisture level:
-lack of water leads to death for both plants and animals, as water is the main component of the blood plasma
-lack of water causes plants to wilt, as water keeps their cells turgid and keeps plants upright
-water is also required for photosynthesis
Soil pH:
-affects biological activity in soil, and the availability of certain minerals
-some plants grow better in acidic soils, such as rhododendrons and ferns
-others grow better in alkaline soils, like cucumbers and cauliflower
Biotic factors:
Food availability:
-more food = healthier organisms = more organisms can breed more successfully = increased population
New predators:
New pathogens:
-when a new pathogen arises, the population has no resistance to it, so they can be wiped out quickly
Competition:
-if one species is better adapted to the environment than another, then it will outcompete it, until the numbers of the lesser adapted species are insufficient to breed
Difference between a decomposer and detritivore
-decomposers are microorganisms
-detritivores are small animals
Describe the importance of interdependence and competition in a community
Competition:
-occurs when organisms need the same resources and need to compete for it
-can be within a species or between different species
-plants may compete for light, space, water and mineral ions
-animals may compete for space, food, water and mating partners
Interdependence:
-how organisms in a community depend on other organisms for vital services
-includes food, shelter, reproduction (pollination, seed dispersal)
-the removal or addition of a species to a community affects populations, as it changes the number of prey/pradators
How do pyramids of biomass work
-shows the relative biomass at each tropic level
-biomass decreases further up the trophic levels
-not all food consumed by an animal is converted into biomass, so the biomass of the organism in the level above will always be higher, as not all the organism can be consumed and converted into biomass
-only about 10% of biomass of each tropic level is transferred to the next, as:
-not all biomass can be eaten, such as bone, hooves, claws and teeth
-lots of glucose is used in respiration
-some might be excreted instead of converted into biomass
-herbivores do not have all the enzymes to digest all the material they eat, so it is egested instead
EQUATION:
efficiency of biomass transfers = biomass transferred to the next level/biomass available at the previous level x100
3 types of ecological relationships (in interdependence)
Predation:
-relationship between a predator and prey species
-if the population of prey increases, there is a larger food supply for predators, so more offspring survive
-the growing number of predators eventually reduce the food supply, so the number of predators decreases
-the prey population starts to increase
Mutualism:
-both organisms benefit
-e.g. bees are attracted to flowers and nectar, so the bees get to eat, while flowers are able to be pollinated to ensure their survival
Parasitism:
-only one organism (the parasite) gains
-the parasite lives off the host, which suffers
-e.g. tapeworms attach themselves to the insides of intestines of animals like humans and cows
-they feed on the host’s partly digested food, depriving the host of nutrients
