Paper 2A Part 2 Flashcards
Define ecology
the study of inter-relationships between organisms and their environment
What sort of factors does the environment include?
- Biotic factors: Living factors2. Abiotic factors: Non-living or physical factors
Examples of biotic factors
Predation, competition, number of mates, disease, prey and predator numbers
Examples of abiotic factors
Soil pH, water availability, space, rainfall, nutrients, light intensity
Define the biosphere
The biosphere is the regions of the surface (land) and atmosphere (air) and earth occupied by living organisms
Describe the biosphere (3 points)
- Shaped by interactions within organisms and environment- An interconnected network- Involved in the study of ecology
Define ecosystem
An ecosystem is all the interacting biotic and abiotic factors in an area
What are the two main components of an ecosystem
- The flow of energy- The cycling of elements
Different ecosytem cycles and what they are
Water cycle – cycling of water (H and O) through the water cycleRespiration – transfer of energy and elementsNutrient cycles – nutrients contain elements (nitrates and phosphates) are recycled in pondPhotosynthesis – plants utilising the suns energy and converting some to ATP/chemical energyDecay – decay of material releases CO2
What is a habitat
A habitat is where the community (different organisms in the same place) is found
Within each habitat there are smaller microhabitats, what are these?
- A habitat which is of small or limited extent- Differs in character from surrounding habitat (own microclimate)
What are the different microhabitats present in a mature fruit tree?
- Leaves, flowers and fruits (different microhabitats throughout year (seasons) and fruit and flowers in specific times of year)- Bark (Lichens and mosses grown on the bark (habitat for them) and different depending on position, shelter age and light intensities = different conditions- Lichens and mosses (provide microhabitat for small insects)- Canopy deadwood (micro-organisms involved in decay found)- Plants colonising the tree base/surface (millipedes, woodlice and caterpillars)
What is a population?
A population is a group of interbreeding organisms of one species in a habitat
.A number of ______ can be found within each ecosystem
species
.Members of the same species group together forming a ________
population
.Different _____ group together to form different populations
species
Population boundaries are difficult to define because organisms move, explain this in more detail
- All herons can breed with one another so form a population- Woodlice on a rotting log on one side of the pond could breed with woodlice on the other side of the bond- If interbreeding is unlikely = two populations
A community is …
… all the populations of different species living and interacting in a particular space at the same time
In the pond ecosystems, the community would consist of:
• Frogs• Herons• Bacteria• Bull rushes• Trees• Grass• Fish• Worms• Insects• Fungi • Snails
What is an ecological niche?
An ecological niche is how an organisms fits into its role within the environment
What does an ecological niche include?
- Where it lives and what it does- The biotic and abiotic factors required for an organisms survival
Why do no two organisms occupy the same niche?
- Different tolerance levels to environmental factors- Best adapted species survives and reproduces- At the expense of the weaker species (if conditions remain stable)- Competitive exclusion principle (two species competing for the same limited resource cannot coexist at constant population values as one will always outcompete the other)
What is population size?
Population size is the number of individuals within a population
What is exponential growth?
- Growth rate is proportional to time- As time increases, the variable being recorded increases- At an exponential rate- But most population growth in the wold does not follow this trend
What is most population growth like?
- Slow growth – initially a small number of individuals to reproduce2. Rapid growth – increased number each reproducingPopulation doubles, increasingly steep curve3. Stable state, no growth – rate of growth declines until roughly stable, the population reaches its carrying capacity
What is carrying capacity?
the number of organisms which an ecosystem can support without environmental degradation
A limiting factor is …
… an environmental condition that limits the growth, abundance, or distribution of an organism or a population of organisms in an ecosystem
Why do limiting factors matter?
Limiting factors prevent the population growing exponentially
What are the main limiting factors?
- Disease- Predators - Water/Humidity - Oxygen - Competition- Food- Light- Shelter - Waste accumulation- Temperature - pH
How are all of the population limiting factors limiting population?
Disease Mutation = no antigens, no memory cellsPredators New adaptations, introduction of species, competitionWater/humidity Transpiration, photosynthesis, osmotic lysis, drought tolerance (GM)Oxygen Respiratory rate, haemoglobin, tertiary structures, affinityCompetition Intra and inter specific, food websFood New sources, global warming, monocultures, deforestationLight Light intensity – photosynthesis, transpiration, food productionShelter Shade tolerance, competitionWaste accumulation Mutations for tolerance, pH changes = enzymesTemperature Enzymes, transpiration, all metabolic processespH Enzymes, tissue fluid, mutations, O2 affinity, metabolic processes
Describe the growth rate in bacteria
.Quick/rapid growth.Asexual reproduction.Less complex.Binary fission
Describe the growth rate in humans
.Slow growth/stabilises.Sexual reproduction.Long development.Few offspring
Describe the growth rate in cats
.Middle term.Long gestation.Multiple births
Is the rate of population change between species the same?
No
When should you use logarithmic scales?
.Rapid growth.Long period of time
Why should you use logarithmic scales?
.Reduces wide-ranging quantities to tiny scopes.Clearer pattern shown
If log x (y) = z then …
… x^z = y
A new pond has formed and some algae cells have been found. Predict what will happen and explain why you think this.Hint, it is summer, there are no nutrients in water, there are no limiting factors, they reproduce asexually
• They reproduce asexually - Reproduction is quick so number rapidly increases• It is summer- High rate of photosynthesis = growth occurs quickly • There are nutrients in the water - Mineral ions used up by increasing population.• There are no limiting factors BUT this changes- Algae on surface block light reaching deep into the pond.- Fewer ions or sunlight available for algae- Other species arrive better adapted to different abiotic factors- Increase competition and/or predation.- Changing seasons = temperature drop and lower light intensity- Algae population decrease
Describe the human population growth with figures
The human population has doubled in the last 50 years. Now over 7 billion. If this rate continues we will double our population in the next 40 years!
What factors are increasing human population growth?
- Health Care – Fewer people are dying/aging population - Infrastructure and resources – More houses/workplaces/stability- Economy – More money for medical care, houses, food - Food availability (Agricultural Revolution) – Better nutrition/growth- Better quality of life – Better hygiene, fewer diseases- Industrial Revolution
.Human population growth does not follow the usual _______ shape
sigmoidal
For human population growth, the exponential phase is still continuing rather than plateauing, why?
- Birth rate outweighs death rate - Immigration outweighs emigration
Population growth =
(births + immigration) - (deaths + emigration)
Percentage population growth rate =
(Population change during time period / population at start of period) x 100
Birth rate is affected by:
• Contraception • Money • Culture and Religion • Social Pressures • Politics (Education and Taxes)
Death rate is affected by:
• Age of population • Life expectancy at birth• Food supply and range• Natural Disasters and War• Water and Sanitation
What is a population pyramid?
.Age and gender profiles are displayed graphically by stacked bars which represent the % age of males and females in each age group
What do population pyramids give information on?
.They give information on future trends of populations, for example how many females of child bearing age
In a population pyramid with a narrow base and wide apex what can you deduce
Lower birth rate = narrower base.Lower mortality rate = more elderly people so apex is wider.Applies to certain economically more developed countries (Japan)
In a population pyramid with a wide base and narrow apex what can you deduce?
High birth rate = wider base.Fewer old people = narrow apex.Typical of economically less developed countries.
In a population pyramid with an in balance birth and death rate what can you deduce?
Birth rate and death rate are in balanceNo change in population size.Typical of economically developed countries.
As countries develop economically, their human populations display a pattern of growth known as what?
demographic transition.
Demographic transitions can be divided into 4 stages depending on what?
- Death Rate - Birth Rate - Total population
What are the four stages in demographic transition and describe them
- Small and stable – high birth rate, high death rate2. Early expansion – high birth rate, decreasing death rate3. Late expansion – decreasing birth rate, low death rate4. Large and stable – low birth rate, low death rate
Draw a demographic transition
check notes
What is a predator?
A predator is an organism that feeds on another organism (prey)
Predators have evolved to become better adapted for capturing their prey, give some examples of adaptations
- Faster- Better camouflage- Sense of smell/eyesight- Claws/teeth- Agile
What is a prey?
A prey is an organism that is attacked/eaten by another organism
Prey have evolved to become better adapted for escaping predators, give some examples
- Camouflage- Concealing behaviour- Speed- Protective features
Explain how prey become adapted for escaping their predators.
New mutations occur within the prey population, those with mutations that are advantageous to escaping the predators survive and reproduce and their alleles are passed on at the expense of the less advantageous alleles.
What is a stable community?
A stable community is where all the species and environmental factors are in balance so that population sizes remain fairly constant
Draw and label a graph that shows the effect of change in temperature on a stable community
Check notes
Describe predator prey cycles
• Predator and prey populations determine one another’s growth• The size of one population has a direct impact on the others• This is a cyclic relationship (recurring in cycles)
Describe the predator prey cycle graph
- The pattern shown is that whenever the prey rises to a peak in population size, the population size of the predator grows soon after (but not to the size of the prey), then then as soon as the population size of the prey starts to drop again, soon the population of the predator will as well, this pattern continues multiple times.
Explain the predator prey cycle graph
- This pattern exists as, since the population of the prey rises, then the predators have more food to eat, so they have more chance of survival, so they can reproduce more, so their populations increase, which means they need more food to maintain their population, so they eat more prey, so the population size of the prey falls, so the predators have less food, so they have less chance of survival, so they reproduce less, so their population falls as well, and now since theirs less predators to eat the prey the prey have a higher chance of survival and so their population rises again and the cycle starts again.
A relationship that is described as cyclical is …
a. Evolving or recurring in cycles – changes in population sizeb. Recurrence in cycles – as one population changes it directly affects another
Cyclical relationships can also be a result of what?
a. Climatic changesb. Disease
The severity of a population crash can be increase or decreased depending on what? Explain each point
- The number of food sources relied upon (If only one food source is relied upon, and it is destroyed, the population will crash/die. If it has other options its likelihood of survival is higher)2. Genetic diversity (Increased probability that there is an advantageous allele in the population)3. Availability of mates (Those with advantageous allele or those who survive can breed easily and increase the population size rapidly. Lack of mates means the population cannot increase)4. Gestation time (asexual or sexual) (Can lots of offspring be produced very quickly after a crash or decline to re-build the population quickly?)5. Intensity of change (Has the environment significantly changed i.e. a drought or is it a period of prolonged dryness that can be survived?)
How can climate change affect cyclical relationships? draw and label a graph
Check notes
Discuss the advantages and disadvantages of using lab studies to investigate predator prey relationships
Advantages –• Control group for comparison• Investigate multiple factors i.e. is it food availability, poaching or both • Difficult to count all organisms in the wild so data is unreliableDisadvantages – • Results in extermination of the prey which would not happen in nature. Why? • Habitats are varied in the wild (could have an effect)• Area the organisms can travel is much larger• Prey can escape predation
Competition arises when …
… 2 or more individuals share any resource that are insufficient to satisfy their requirements
What do animals compete against?
space, mates, food and minerals, light, territory and water
There are two types of competition, what are they? With examples
- Intraspecific (same species) i.e. mates2. Interspecific (different species) i.e. space/food
Why is intraspecific competition important?
• The availability of resources determines the population size as the greater the availability, the larger the population size as there are more resources to grow and breed
Some oak trees have just started to grow. They are competing for light, water and nutrients. Only some survive. Which will survive and why?
• Mutation occurs• Mutation is advantageous (causes leaf to have larger leaves or extended roots)• Organisms is better adapted to access the requirements for photosynthesis• Organisms grows and survives to reproduce• Frequency of allele increases in subsequent generations • At the expense of the smaller leaved plants
Examples of intraspecific competition
- Limpets, competing for algae (food) 2. Oak trees, many small trees, some grow and block light, smaller ones dies, left with few large, dominant oaks3. Robins, breeding territory, females only mate with males with territory, each territory only supports one family, scarce food, territories become larger
What occurs in interspecific competition?
• Populations of 2 different species initially occupy the same/very similar niche BUT…..• One will normally have a competitive advantage over the other so….• Best adapted survives and breed• Population increases at the expense of the weaker, less adapted species, resulting in…..• Complete removal of the weaker species
What is the competitive exclusion principle?
No two species competing for limited resources can co-exist (or occupy the same niche) as one will always eliminate the other
Example of competitive exclusion principle
• Red : Native to UK• Grey : Introduced from America• 2.5 million grey squirrels and only 160,000 red.
Describe and explain the relationship between red and grey squirels
• More grey squirrels, less red squirrels as competing for food, habitats and space• Number of predators increase, grey squirrels do not increase in number as predators eat grey squirrels but the ones alive still outcompete red• As predation decreases, population of red squirrels decrease and grey squirrels growth slows, grey squirrels are not eaten but more competition within grey
It is often difficult to prove that competition is the factor affecting population sizes, why?
- Many other factors involved (abiotic)2. A causal link has to be established3. Often a time lag (population change may be due to competition that took place many years earlier)4. Data on population sizes are hard to obtain and not always reliable
What is abundance?
the number of individuals of a species in a given space
How do we measure abundance?
.Study small sections of the habitats in detail
Sample methods include:
- Random sampling in the form of frame quadrats and point quadrats- Systematic sampling along transects
What do quadrats do?
investigate the difference between two or more sites
Three key factors need to be considered when using quadrats:
- The size of the quadrat to be used2. The number of sample quadrats to record within the study area 3. The position of each quadrat within the study area
Why the size of the quadrat being used is important –
.Size of the species being studied .Size of the area being studied.Are species evenly distributed or clustered in small groups? If not, a large number of small quadrats is representative
Why the number of sample quadrats to record within the study area is important –
.Larger sample = more reliable the results.Number of species present in the sample area.Larger number of different species in the sample, the greater the number of quadrats required to produce valid results
Why the position of each quadrant within the study area is important –
.Sampling must be random
To ensure that observer bias is minimised, you must generate the positioning of your quadrats in what way?
Randomly
How do you do random sampling with quadrats?
- Two long tape measures at right angles along 2 sides of the study area.2. Use coordinates by using random numbers from a table/computer3. Place a quadrat at the point of intersection4. Repeat multiple times
Sampling with quadrats must be random in order to –
- Avoid sampling bias- Ensure data obtained is valid- Produce statistically significant results
You have been provided with frame quadrats of varying sizes: - 0.5m2, 1m2 or 4m2Using this equipment, suggest how you could use a frame quadrat to investigate the effect of grazing animals on the number of plants growing in a field. (5 marks)
- Choose a quadrat of appropriate to the size - plants are quite small but area is quite large so 1m2 would be most suitable2. Choose 2 fields close together as this minimises soil, climatic and other abiotic differences 3. One site is regularly grazed, the other is not4. Take random samples at many sites in each field either by dice, random number generator, co-ordinates out a hat5. Place the quadrat on the ground and record the names and numbers of the different species present6. Repeat to increase reliability and calculate a mean
What are point quadrats and how are they used?
• Horizontal bar supported by 2 legs.• Pins are dropped through holes in the top• Each species the pin touches is recorded.
Difficulties of using quadrats include –
.Difficult to identify and count every organism.Time consuming.May damage the habitat..Difficult to avoid introducing an element of personal bias.No indication of pattern
Advantages and disadvantages of point quadrats?
NAME?
Economic Advantages –
.Construction sites, less environmental costs.Finding the optimum conditions for horticulture.Finding the optimum conditions for agriculture
Systematic sampling studies what?
The distribution of a species
When is systematic sampling important?
.Gradual changes occur across a habitat.Transitions within communities occur.Zonation is present
What are the two types of transect?
.Belt transect.Line transect
What is a line transect and how does it work?
.String or tape.Organisms over which the line passes are recorded.Usually using a quadrate
What is a belt transect and how does it work?
.Strip or meter wide tape.Second placed parrall to the first.Species between the two belts are recorded
Line Transect Adv and DisAdv –
.Limited Time (Quick).Easily shows species range along the transect.Clear visual of how species change.Harder to see the range across a large area.Less data collected
Belt Transect Adv and DisAdv –
.More data.Tells you more about the abundance AND range of individual species at different points along the line .Shows changes/distribution more clearly as more data.Dominance of one species can be determined.Larger area covered.Time Consuming
.Transects show what?
change in the number of species over a given area.It is not a comparison between two area.It is used to show a trend
How to use a transect?
- Place a transect (tape measure) down across a given area2. Place a quadrat down at equal or random intervals along the transect3. Carry out a second transect in a different part of the sample are but still close by your first sample, so that there is not too much variance in the environment as to change the results massively4. Calculate a mean across the 3 transects studied and display your results in a table5. Plot a graph and describe the pattern shown
Abundance is …
… the number of individuals in a given space
Frequency is what?
.The likelihood of a particular species occurring in a quadrat
Percentage cover is what?
.Estimate of the area within the quadrat that a particular plant species covers
Equation for per quadrat?
Per quadrat = (number of squares species occurs / number of squares in total) x 100
Adv and disadv for frequency?
Often expressed as a %Useful where a species is easier to countA quick idea of the species presentLacks information on the densityNo detailed information distribution of a speciesCan be quite time consuming
Adv and disadv for percentage cover?
Useful when a species is abundant or difficult to countData can be collected quicklyGives a representation of distribution/densityLess useful where organisms occur in overlapping layersCan be less preciseOften subjective
What does mark, release, recapture method entail?
- A specific number of animals are caught, marked and then released2. After some time, a given number of animals are collected randomly3. The number of marked animals counted
Estimated population =
(total number in 1st sample x total number in 2nd sample) / number of marked individuals recaptured
- Not all organisms will have equal chance of being caught as …
… they might have different adaptations to make them more camouflaged/escape
Mark, release, recapture is the best option when
- Live organisms- Large areas to sample- Focus of one species
The mark, release, recapture method is based on a number of assumptions, list them along with why the assumptions are important:
- Proportion of marked to unmarked in the second sample is the same as the proportion of marked to unmarked in the whole population – results not due to different sizes of sample2. Marked individuals distribute evenly – results are valid and not in clusters3. The population has a definite boundary – you are studying the whole population4. Markings are nontoxic and makes it no more conspicuous – do not injure of reduce the survival chances5. Population is constant e.g. not breeding season – ‘new’ individuals would not be marked6. Markings cannot be rubbed off during the investigation – population size in second sample is not reduced = valid
Why is mark, release, recapture useful for measuring abundance with organisms?
When organisms can move, hide, and are difficult to find and identify
What are the disadvantages of the mark, release, recapture method?
Time consuming (need to leave time)Risk of predation changing sample sizeDisturbance of habitatTrauma or injury to the organism (ethics)
What is meant by positive cooperativity?
- The binding of the first oxygen to haemoglobin makes the binding of the second and then third easier
What is meant by the term competitive exclusion principle?
- Organisms will compete for the same resources, the better adapted will survive at the expense of the weaker
Succession is what?
the change in species in an area over time
Is succession fast or slow?
It can be either
Does succession occur in plants or animals?
Both
Where is succession seen?
- Seen in a range of environments:.Silt/mud deposits at estuaries.Lakes/ponds created by land subsiding.Sand forming dunes
At each stage in succession, certain species change the environment so …
it becomes more suitable for other species with different adaptations
What is a pioneer species and climax community?
Pioneer species (a species colonises an inhospitable area, the first one)Climax community (stable community, very little/no change, the last one)
Pioneer Species tend to have what characteristics?
- Reproduce asexually 2. Produce large quantities of wind dispersed seeds or spores3. Can tolerated/are adapted to survive in harsh conditions i.e. low light intensities, low/high pH4. Short dormancy or fast germination5. Photosynthesise 6. Are nitrogen fixing
Why does pioneer species have those characteristics?
.They reproduce asexually so that they do not rely on another species to increase its population size.They produce large quantities of wind dispersed seeds or spores so that they can spread to remote areas and without the need for other organisms .The can tolerate harsh conditions so that they can survive and reproduce when no other organism can.They have short dormancy/fast germination so that they can reproduce/increase in number quickly.They can photosynthesise so that they do not rely on food sources.They are nitrogen fixing so they improves soil quality in when few nutrients
(S) Explain the process of succession, using both animals and plants as an example of this (6 marks)
- Pioneer species colonises inhospitable area2. Reproduces = increases3. Changes the conditions/a species makes the conditions less hostile;4. New/primary coloniser is better competitor/pioneer species outcompeted; Example = Lichens 5. Pioneer species grows, dies and nutrients are recycled via decay6. Increase in secondary coloniser, changing abiotic factors further7. Better adapted/tertiary species increases and secondary decreases8. Process continues until a climax community is formed9. Few if any new species are replaced
What is the process of succession?
- Pioneer SpeciesColonises harsh environmentReproduce and increase population size Changes the environment – nitrogen fixingImprove soil quality2. Primary Coloniser – for example Lichens who colonise bare rock and can survive desiccation (extreme dryness)New species better adaptedOutcompete pioneersNew community forms Continue to change the environment (abiotic factors) to make it less hostile3. Secondary ColoniserWeathering of the rock creates sand and soilLichens die and decomposeNutrients are recycledNutrients support small plant species• The quality and quantity of the soil improves • Rock erosion continues and plant species die and decompose.• The smaller plants again change and improve the abiotic factors• The area can support larger species: grasses, shrubs then trees.• Continues until the climax community is reached.
Animal populations establish and grow in the _______ process
Cessionary
Describe animal succession?
Animals are still reliant on the pioneer plant speciesLichen dies and provides food for detritus feeders Mosses and grasses provide food and habitat for insects Secondary consumers feed on the insects Flowering plants and trees support reptiles, mammals and birdsThey are still reliant on lichens to provide primary colonisers with food
Climax communities have dominant _____ and ______ species
plantanimal
If an area of land has experienced land clearance or a natural disaster the area returns to its climax community but:
- It does it much faster as the seeds and spores are already present therefore it does not begin at a pioneers species - The climax community will be different as there are different abiotic factors
Define preservation
Maintaining individuals, populations and ecosystems in their current state without the exploitation of their natural resources
Define conservation (and the two types)
Allowing ecosystems to evolve (change) naturally, without resources being overused, there is active human management and two forms:- Ex-situ:Individual endangered species in zoosOutside natural habitat- In-situ:Whole ecosystems and landscapesWithin habitatMonitoring succession
Why do we manage succession?
• Allows ecosystems to evolve naturally• No detrimental effects on any stage of succession• Enables maximum diversity and ecosystems
Explain the stage of succession that should be of greatest focus to conservationists.
- Mid Succession2. Not dominated by one species (low diversity) 3. Not a very hostile environment4. Can support multiple species, more habitats/food sources = higher biodiversity
Why is the stage of succession that should be of greatest focus to conservationists not the climax community?
- Dominated by one species- High competitive element- Competitive exclusion principle- Low Biodiversity
How does burning heathlands manage succession?
- SOME areas are burnt = Prevent succession2. Prevents dominance/climax community3. Older forms are less palatable and less nutritious 4. New heather and other new species can grow5. Biodiversity is increased
Burnt vs Unburnt areas create more:
- Habitats- Food sources- Species
How is succession controlled in moorlands? Why?
• Grazing by sheep and/or periodic burning• Maintains low growing plant populations• Provide plentiful food sources for grouse• Increases number of grouse • Happy hunters!
Explain what may happen to moorland if sheep grazing and burning of vegetation ceased? (3 marks)
- Moorland would undergo secondary succession Moorland would reach its climax communityCommunity would be dominated by deciduous oak woodland (one species) Reduction in biodiversity
Suggest how conservation and leisure could be managed (2 marks)
- Hunters pay to shoot/only allowed at given timesPayments control and coordinate conservationist burning the land
Discuss the importance of studying and understanding conservation and enhancing biodiversity
- Money - Medicines - Tourism - Wood- Food - Horticulture- Removal of CO2
Define genepool
all the alleles of all the genes of all the individuals in a population at a given time at a given time
What is natural selection?
the process by which organisms that are better adapted to their environment tend to survive and breed at the expense of those less well adapted.
