5B: Ecology Flashcards
5B.1 - 5B.7
Define Ecology
- the study of the interactions between organisms and their environment
- these interrelationships determine the distribution and abundance of organisms and their environment
What does the life-supporting environment of an ecosystem include:
- all the living organisms interacting with it
- the nutrients that cycle throughout the system
- the physical and chemical environment in which the organisms are living
What does an ecosystem consist of?
a network of habitats and the communities or organisms associated with them
What is a habitat and a microhabitat?
the place an organism lives
a small area of a habitat
What is a population?
a group of organisms of the same species living and breeding together in a habitat
What is a community?
all the populations of all the different species or organisms living in a habitat at any one time
What is a niche?
the role of an organism within the habitat in which it lives (its profession)
several organisms can share the same habitat, occupying different niches
What are abiotic factors + examples?
non-living elements of the habitat of an organism including those related to the climate and soil (edaphic):
- amount of sunlight
- temperature
- rainfall
- drainage (soil)
- pH (soil)
- oxygen availability (in aquatic environments)
What are biotic factors?
the living elements of a habitat that affect the ability of a group of organisms to survive there
What is the biosphere and biomes?
biosphere is all areas of the surface of the Earth where living organisms survive
they’re divided into smaller parts distinguished by similar climates and plant communities called biomes (major ecosystems of the world)
Define succession
the process by which the communities of organisms colonising an area change over time
When does primary succession occur?
after a volcanic eruption, landslide, or after emergence of new volcanic island
What does primary succession start with?
starts with empty inorganic surface such as bare rock or a sand dune
What is the first stage of succession?
colonisation: process by which new species spread to new areas
What organisms are the first to appear in succession and why?
opportunists / pioneer species like algae, mosses, fungi
as these organisms can penetrate the rock surface by:
- dissolving rock with acids they secrete
- penetrate tiny cracks with root hairs and hyphae
What is the start of soil formation?
- after pioneer organisms penetrate rock surface, this helps break rock into small grains, and trap organic material that breaks down to form humus
- inorganic rock grains and organic humus are the start of soil formation
What happens during succession after there is soil?
- species like grass and ferns can establish root systems
- the action of their roots and humus they form when they die and decay add to the soil
What happens as the soil layer continues to develop during succession?
- as soil layer develops, more water and nutrients are kept and become available for plant roots meaning less resistant species survive
- gradually, larger plants can be supported and species diversity increases resulting in an increase in diversity of animals that can be supported
When do we reach a climax community?
a climax community is reached in which the biodiversity and range of species are generally constant
it’s self sustaining and the most productive group of organisms the environment can support
What is a plagioclimax?
a sub-climax community where succession has been held back / deflected by human activity
climax community can develop when humans move away
What is secondary succession and when does it occur?
the development of an ecosystem from existing soil clear of vegetation
occurs after fires, floods, disturbances caused by humans
there are a higher number of plants from the start
What factors does the time taken to go from bare Earth to a climax community depend on?
- temperature
- rainfall
- soil fertility
What is a climatic climax community?
the only climax community possible in a given climate
What is the effect of light (abiotic factor) on populations?
amount of light in a habitat has a direct effect on no. of organisms found there
What are some adaptations of plant populations that grow well in low light level habitats (such as plants in understory of rainforest) ?
- reproduce early in the year to avoid shade of larger plants in summer
- extra chlorophyll
- different ratio of photosynthetic pigments sensitive to lower light levels
- very large leaves to absorb light
How are animals indirectly affected by light levels?
- as a result of distribution of food plants
- seasonal light changes affect reproduction patterns in some
- animals are affected by 24 hour cycle of light and dark and this influences natural rhythms that control much animal physiology and behaviour
………. … ………. determine where an organism can live
extremes of temperature
How does the temperature of the environment affect plants and animals?
it affects the rate of enzyme-controlled reactions in plants and ectothermic animals like reptiles
What have animals evolved to help them deal with extreme temperatures?
animals have evolved behaviours and physiological adaptations
What effect does wind have on organisms in a habitat?
wind has a direct effect
What is the relationship between strong prevailing winds and the number of species that can survive in such conditions + why?
Wind increases cooling and water loss from the body so increasing environmental stress
Fewer species can survive in areas with strong winds
What is the effect of gales (strong winds) and hurricanes on populations?
- they cause extreme damage to populations; whole woodlands may be destroyed and communities of plant and animal life within them lost
How do organisms survive in water where there are currents?
- flow with the current
- be strong swimmers
- be able to attach to a surface and resist force of water
When are (water) currents most damaging to populations?
when strength increases suddenly such as flooding
What is availability of water in terrestrial environments affected by:
- amount of precipitation
- rate of evaporation
- rate of loss by drainage through soil
What can an increase in availability of water lead to in populations + why?
- It can lead to a huge increase in population size of some organisms
- as this provides optimum food conditions for insects and organisms that manage to survive in difficult conditions, so there is a population explosion!
How do we know if water has enough oxygen content in it?
When water is cold or fast flowing, there’s enough oxygen dissolved in it to support life
If water temp rises or no longer flows, oxygen content drops
How do plant roots obtain air from the soil?
As spaces beteeen soil particles contain air
What is the adaptation for plants that can survive in waterlogged soil?
Aerial roots allow plants to grow successfully even if air spaces in soil are filled with water
What are edaphic factors?
Soil structure and mineral content
What type of soil structure does sand have?
Sand has a loose, shifting structure allowing little to grown on it
What type of plant populations survive on sand and how?
Plant populations linked by massive root and rhizome networks e.g. dune grass
They reproduce successfully and bind sand together making it more suited for colonisation by other species
What are adaptations of leaves of plants in the desert?
They curl round themselves with the stomata on the inside, creating a microenvironment that reduces water loss
Features of soils that contain a high proportion of sand
- light
- easily worked
- easily warmed
- very easily drained
- leaching of minerals reduces population density of plants that can grow in the soil
Features of soil predominantely made up of small clay particles
- difficult for water to drain through
- heavy
- hard to work
- easily waterlogged
- no problem with mineral leaching but population it will support is limited
Features of ideal soil (loam); has particles in a wide range of sizes
- heavier
- leaching less likely
- easier to warm and work
What is the relationship between prey and predator populations?
Populations will oscillate (change between 2 extremes) in a repeating cycle
1st stage of prey-predator population cycle
As a prey population increases, there is more food for the predators so after an interval, the predator population grows too
2nd stage of prey-predator population cycle
Predators will increase to the point at which they are eating more prey than are replaced by reproduction, so numbers of prey will fall
3rd stage of prey-predator population cycle
Number of prey fall so this reduces food supply of the predators so they will not produce as much offspringand their numbers will fall, allowing abundance of orey to increase again and so on
What is the pattern in a prey population where there are no predators?
They follow a similar pattern to prey-predator population cycle
They respond to cycles in their food availability that are related to climatic variations and changes in insect pest populations
Probability of ….. .. ….. (or achieving ……..) affects which organisms are found in any habitat
Finding a mate
Polination
A single individual of any animal species in an area doesnt mean the species ….. in that habitat
Lives
What is the abundance of any type of animal that reproduces sexually found in an are greatly affected by?
Availability of mates
Define territory
An area held and defended by a group of animals (same or different species) against other organisms
What are territories used for?
To make sure that a breeding pair have sufficient resources to raise young
What does the type and size of a territory help determine?
It determines which species live in a particular community
What is the affect of disease on all animals?
Diseased animals will be weakened and often do not reproduce successfully
What is the affect of disease on predators and on prey?
Sick predators cannot hunt well
Diseased prey animals are more likely to be caught
What is the affect of parasites and infectious diseases in high population density areas?
They spread rapidly as individuals are close together
What is the effect of an infectious disease in an area of high population density where almost all organisms in the area are of the same species?
Worst case as it will affect most induviduals directly or indirectly rapidly
What is the effect of an infectious disease in a community of greater biodiversity?
Much less of an effect although individual effect will be the same
Many species will be unaffected and there will be plenty of alternative food options
The abiotic and biotic factors that affect the number of organisms occupying a particular niche may be:
- density-independent factors (tend to be abiotic but can be biotic)
- density-dependent factors (tend to be biotic)
Describe effect of density-independent factors in relation with population size
Effect of density-independent factors is the same regardless of population
Examples of density-independent factors
- natural disasters
- soil conditions
- deforestation
- climate
- global warming
How do density-independent factors affect distribution
They limit distribution of individuals and therefore species
What do density-dependent factors depend on?
They depend on how many organisms there are in a specific area
Examples of density-dependent factors
- competition
- food shortages
- predation
- disease and parasitism
- breeding / habitat space
Relationship between disease and individuals in a given area
More individuals in a given area , the more likely a disease can be transmitted between individuals
How is breeding success in territorial animals density dependent?
As individuals without territories are less able to breed
Only strongest individuals are able to hold territories if space is a limited ressource
What are density-dependent factors important in?
In limiting abundance of species
Individual organisms often have to compete for …… …….. factors
Thus can determine the ….. and …… of a population
Density dependent
Size and density
When does competition occur?
When 2 organisms compete for a resource that is in limited supply
Could be biotic or abiotic
What is intraspecific competition?
Competition between members of the same species for a limited resource (within the same niche)
What may happen as a result of intraspecific competition?
Individuals may not survive
What is interspecific competition?
Competition between different species within a community for the same resources(niches of the species overlap)
Competition reduces …… of competing species
Abundance
Define abundance
Relative representation of a species in a particular ecosystem (relative to no. of other organisms in the same habitat)
Define distribution
Where a species of organism is found in the environment and how it is organised
How may distribution of organisms change?
Animals might migrate
Some organisms are always found in very high densities
Other species are found spread throughout a habitat (top predators)
Describe uniform distribution
Occurs when resources are thinly but evenly spread or
when individuals of a species are hostile to eachother
Territories may be very large or small
Describe clumped distribution
Most common with groups of plants and animals that clump together in areas where their specific resource requirements are found
Describe random distribution
Result of plentiful resources and no hostility
What is a null hypothesis?
a hypothesis that any differences between data sets are the result of chance
