7C Flashcards
What is an Ecosystem?
All organisms living in a community, plus all abiotic and biotic conditions
What are Biotic Conditions?
Living features of an ecosystem, E.g. the presence of predators or food
What are Abiotic Conditions?
non-living featured of an ecosystem, such as temperature and soil
what is a habitat?
a place within an ecosystem, where an organism lives
within a habitat, each species has its own niche, what is a niche?
the role of a species within its habitat, E.g. what it eats, where and when it feeds etc.
The Niche a species occupies includes:
- biotic interactions - E.g. the organisms it eats, and those its eaten by
- Abiotic interactions - E.g. the temperature range an organism can live in, the time of day when an organism is active
if two species occupy the same niche, what will happen?
one species will be more successful than the other, until only one species is left
what is an adaptation?
an adaptation is a feature (change in allele) of a species which increases their chance of survival and reproduction
what types of adaptation can there be?
behavioural (way the organism acts), mechanical (structural) or physiological (process within their body)
E.g. giraffes have long necks to help them reach vegetation that’s high up. organisms with better adaptations are more likely to survive and reproduce, passing on their advantageous alleles
when organisms pass on their advantageous alleles to their offspring,, increasing the frequency of the alleles in the population, making the adaptation more common, what is it called?
Natural Selection
what is a population?
all the organisms of one species in a habitat
populations of different species in a habitat make up what?
a community
‘when the maximum stable population size of a species that an ecosystem can support’ is called…
a carrying capacity. it varies as a result of both abiotic and biotic factors
Abiotic factors and population size
The population size of any species varies due to abiotic factors, e.g. amount of light, temperature, water supply, wind. When these conditions are ideal for the species, organisms can survive, grow and reproduce. However when the abiotic factors aren’t ideal, the organisms can’t grow or reproduce successfully
IntERspecific competition
organisms of a diffERent species compete with another for the same resources - this can mean the supply of the resources is reduced. if there’s less resources available (Food) then there’s less food energy for growth and reproduction; so pop. sizes will decreases for both the species. the best adapted species will eventually outcompete the other species
intrAspecific competition
Organisms of the sAme species compete against each other for the same resources. This causes a Cyclical change in the pop. size around the ecosystems carrying capacity (pop. size grows, shrinks, grows) as the pop. inc. when resources are plentiful, but pop. then goes beyond carrying capacity, eventually dec. when resources are low. the pop. will then be low enough for resources to be plentiful and the cycle begins again
the cyclical pattern
picture needed
Predation
The pop. of predators and prey are interlinked, as one pop. changes it causes the other to change. as prey inc. more food for the predators - which grow and reproduce. With more predators, prey pop dec. and less resources for the predators, so their pop. dec. so prey pop. inc.
Predator-Prey relationship
picture needed
growing bacteria in a liquid broth - a liquid containing nutrients needed for the bacteria to grow is called…
a broth culture
Spectrophotometer
When light is passed through a sample of broth culture, it is scattered because bacteria are present, reducing the amount of light passing through. Spectrophotometer measures the amount of light and produces an absorbance value. The more bacteria present, the higher the absorbance and vice versa.
plotting spectrophotometer graphs
plot absorbance against time, it is called an exponential graph - showing the bacteria doubling in number at regular intervals. As the absorbance is proportional to the number of bacteria, plot the log number of bacteria against time (easier to plot)
how to work out the Antilog
- press shift log (gives you 10 x )
- place the log number of bacteria and press enter
what is abundance?
Abundance is the number of individuals of one species in a particular area.
how to measure abundance
- it is estimated by counting the number of individuals in samples taken
- the frequency - number of samples the species is recorded in
- percentage cover (non/slow motile organisms) how much of the investigated area os covered by the species
what is distribution?
where the particular species is within the investigated area
random sampling
- divide the field into a grid and use a random number generator to generate co-ordinates. This ensures it is picked randomly.
- the number of individuals for the whole area can be estimated by taking a mean of the data collected in each sample and multiplying it by the size of the whole area.
running means
work out the mean of all the data each time you collect a new sample. once the mean no longer changes by a large amount, that should give a realistic estimate for the whole area.
methods for investigating populations
Quadrats, transects, capturing motile organisms or mark - release - recapture
Quadrats
Can be used to measure the population of slow/non-motile organisms. They’re placed randomly on the floor (or by coordinates and a random number generator)
The number of species present in each quadrat is recorded. The % cover can also be measured by counting how much of the quadrat is covered (more than half a square can be counted)
Transects
Also used to measure the population growth of slow/non-motile organisms. However they also help find how organisms are distributed across an area.
Belt Transects
quartets placed next to each other along a transect line to work out the species frequency and percentage cover along the Transect
Interrupted Belt Transect
quadrants are placed at regular intervals, making it easier to cover larger areas.
capturing motile organisms
capturing should be done ensuring the organism is not hurt, using equipment like: nets (sweep nets for flying insects) or a pitfall trap, trapping insects in a container sunken into the ground.
Mark-Release-Recapture
- Capture the organism with an appropriate technique
- Marking the organism in a harmless way
- Releasing the organism back into their habitat.
- waiting an appropriate amount of time for the organism to fully be back into its habitat and ‘mix’ with other (same species) organisms
- Capture another sample of organisms from the same pop. and count how many are marked from the first sample
Mark-Release-Recapture equation
No. caught in 1st sample x No. caught in 2nd sample / number marked in 2nd sample
The Accuracy of the Mark-Release-Recapture method depends on…
- Marked sample has had enough time and opportunity to mix back in with the population
- Marking hasn’t affected the individuals chances of survival (more visible to predators) and the markings can’t be rubbed off/removed
- No changes in population size (no births, deaths, immigration, emigration etc) during the study
Investigating the Effect of an Environmental Factor on the Distribution of a species
- Place a tape measure in a straight line from the shore to the heading inland - this is your Transect.
- Take a 1m2 quadratic (that’s divided into 100 squares)
- Start from the shore and place a quadratic next to the tape measure
- Count the squares containing marram grass and record the results as a percentage cover.
- At each measure point, measure the pH and record the results
- Repeat every 10m along the transect (interrupted belt transect)
What is Succession?
Ecosystems are Dynamic - constantly changing, Succession is the process by which an ecosystem changes over time. It happens in a series of stages, from a hostile environment, changing to conditions more suitable to other species with different adaptations - meaning abiotic and biotic conditions change
Primary Succession
Primary Succession occurs on land that’s been newly formed or exposed. Theres no soil or organic material to start with (E.g. bare rock)
What is the Pioneer stage of Succession?
Primary succession starts when a species colonise on a new land surface. Seeds and spores are blown in by the wind and begin to grow. The first species to colonise the area are called the pioneer species. Abiotic conditions are hostile/harsh and only pioneer species can grow because they’re specially adapted to cope with the harsh conditions
Examples of Hostile Conditions
- limited amount of water as there’s no soil to retain the water
- Few minerals or nutrients
- High might intensity, exposure to wind and rain, and fluctuating temperatures because the area is directly exposed to the sun and the elements
Examples of Pioneer species
- Marram grass and grow on sand dunes near the sea because it has deep roots to get water and can tolerate the salt environment
- Lichens are organisms usually made up of fungus and alga, surviving rocky conditions
- Shrubs
How do Pioneer species change the Abiotic conditions?
When they die, microorganisms decompose the dead, organic material (Humus) which forms a basic soil, making the conditions less hostile (It can retain water) so new organism with different adaptations can move in grow
What occurs for Succession to take place from the Pioneer species?
The new organisms then die and are decomposed, they add more organic material, making the soil deeper and richer in minerals, such as nitrates. Nitrogen-fixing bacteria turn Nitrogen from the atmosphere into Ammonia. This forms ammonium ions in solution that can then be used by plants.
The Last Stages of Succession
At each stage, different plants and animals that are better adapted for improved conditions move in, out-compete the plants and animals that are already there, and become the dominant species in the ecosystem.
At succession goes on, the ecosystem becomes more complex, increasing the biodiversity, eventually these changes result in a climax community - an ecosystem supporting the largest and most complex community of plants and animals.
What are the dominant species?
Dominant species are the ones which cause the most change to the abiotic environment, making it more suitable for other species.
What is Secondary Succession?
Happens on land that’s been cleared of all the plants, but where the soil remains (Forest fire, deforestation, flood etc.), being less hostile for the pioneer species
Human Impacts on Succession
Human Activites can prevent succession, stopping a climax community from developing. When succession is stopped artificially like this the climax community is called a Plagioclimax
What is Conservation?
Protection and management of species and habitats in a sustainable way.
Conservation Methods - Management of Succession
- Animals are allowed to graze on the land
- Seed banks - storing seeds from lots of different species
- Captive breeding - Breeding animals in controlled environments if the species is endangered or already extinct in the wild
- Fishing Quotas - Limiting the amount of certain fish that fishermen can catch, to conserve the fish species
- Protecting Areas - National parks, and nature reserves, protection habitats and the species in them by restricting urban development, industrial development and farming
What are Point Quadrats?
They consist of a number of metal pins in a wooden or metal frame. The species touched by the needles are scored
