Genetics, Populations, Evolution & Ecosystems 3.7 Flashcards
Populations in ecosystems (AO1)
Define abiotic factor
A non-living / physical / chemical factor
Populations in ecosystems (AO1)
Examples of abiotic factors
soil pH
temperature
salinity (concentration of salt)
carbon dioxide concentration
humidity
light intensity
Populations in ecosystems (AO1)
Define biotic factor
Living / biological factor
Populations in ecosystems (AO1)
Examples of biotic factors
predator
prey / food
disease
presence of opposite sex
Populations in ecosystems (AO1)
Define population
Groups of organisms of the same species living in the same habitat / ecosystem at the same time;
They have the potential to interbreed;
Populations in ecosystems (AO1)
TRUE OR FALSE
Organisisms of the same species that make up a population have the potential to interbreed
TRUE
They will produce fertile offspring
Populations in ecosystems (AO1)
Define community
All the populations of the different species in the same habitat / ecosystem at the same time
Populations in ecosystems (AO1)
Define ecological niche
The role played by an organism in a
habitat/ecosystem governed by adaptations to biotic/abiotic factors
Populations in ecosystems (AO1)
Explain the advantage of different species occupying different niches (1 mark)
Reduced (interspecific) competition for food/resources
Populations in ecosystems (AO1)
Define carrying capacity
Certain size of population of a species that can be supported by the ecosystem
Populations in ecosystems (AO1)
What can reduce carrying capacity?
Habitat loss;
Reductions in food availability;
Increases in the number of predators;
Disease
Populations in ecosystems (AO1)
An ecosystem supports a certain size of population of a species, called the [1] capacity. There are often numerous habitats within an ecosystem. Within a habitat, a species occupies a [2] governed by an adaption to both [3] and biotic conditions. Populations of different species form a [4].
[1] carrying
[2] niche
[3] abiotic
[4] community;;
Populations in ecosystems (AO1)
Ecosystem definition
The interaction between a community and the abiotic components of the environment
Populations in ecosystems (AO1)
Competition between organisms of the same species is known as _________________ competition
intraspecific
Populations in ecosystems (AO1)
Competition between organisms of different species is known as _________________ competition
interspecific
Populations in ecosystems (AO1)
What term describes populations of different species living in the same habitat?
Community
Populations in ecosystems (AO1)
Describe and explain what typical patterns emerge when plotting the population sizes of predators and their prey over time (3 marks).
As prey populations increase, there is an increased availability of food for the predator population;
This causes a (delayed) increase in predator population;
Due to the increase in predators, the prey population
will decline;
A decline in prey populations leads to a shortage of food for the predators, and over time their population will also decline;
This decline reduces the predation on the prey population, allowing for interbreeding and an increase in the population size
(and repeat)
Populations in ecosystems (AO1)
In northern India, there is a conflict of interests between farmers of livestock (eg cows) and people trying to conserve ibex (a type of wild goat).
When livestock are given extra food, their populations can grow too large and compete with ibex.
Name the type of competition between livestock and ibex.
Interspecific
Populations in ecosystems (AO1)
Random sampling reduces __________
bias
Populations in ecosystems (AO1)
Random coordinates are produced using a ________________________
random number generator
Populations in ecosystems (AO1)
Measurements made within quadrat(s)
Number of individuals;
% cover;
Species richness;
Index of biodiversity;
Populations in ecosystems (AO1)
Why use percentage cover rather than frequency / number of individuals to count algae.
Difficult / too many to count / individual organisms not identifiable / too small to identify/count / grows in clumps;
Populations in ecosystems (AO1)
The sundew is a small flowering plant, growing in wet habitats such as bogs and marshes.
Describe how you could estimate the size of a population of sundews in a small marsh (4 marks).
1. Use a grid;
2. Use random number generator for random coordinates (for quadrats);
3. Large sample of quadarts (20 or more);
4. Add the total number/frequency in a quadrat and divide by number of quadrats;
5. Valid method of calculating total number of sundews, e.g. mean number of plants per m^2 multiplied by number of m^2 in marsh;
Populations in ecosystems (AO1)
Describe how you would determine the mean percentage cover for beach grass on a sand dune (3 marks).
1. Use random number generator for random coordinates (for quadrats);
2. Large number of quadrats (20 or more);
3. Divide total percentage by number of quadrats;
Populations in ecosystems (AO1)
Outline a method the ecologists could have used to determine the plant species richness at one site (3 marks).
1. Use random number generator for random coordinates (for quadrats);
2. Large number of quadrats (20 or more);
3. Count number of different plant species (in each quadrat)
Reject refs to % cover, or counting individuals
Species richness = all the different species (AS content)
Populations in ecosystems (AO1)
In addition to a quadrat, what piece of equipment do you need to undertake systematic sampling?
Line / belt transect
Populations in ecosystems (AO1)
In systematic sampling, quadrats are placed on a transect at ____________ intervals
regular
Populations in ecosystems (AO1)
What type of analysis can systematic sampling using a line or belt transect allow you to undertake?
The impact of an environmental gradient on a population size.
Populations in ecosystems (AO1)
Lettuce is classified in the same family as dandelions. Dandelions commonly grow on roadside verges and may accidentally be sprayed with salt when salt is added to the road in winter.
Describe how you could use a transect to investigate whether the distribution of dandelions changed with increased distance from the road (4 marks).
- Lay tape / rope at right angle / perpendicular to road;
- Take samples at regular intervals;
- Using a quadrat;
- Count numbers / percentage cover of dandelions;
- Use several transects;
Populations in ecosystems (AO1)
Suggest one precaution needed when marking the pine martens (during mark, release & recapture) to make sure the estimate of the number of pine martens is valid (1 mark).
(Marking) does not affect survival/predation/recapture (of the pine marten);
OR
Mark does not rub/wash off/is non-toxic.
Populations in ecosystems (AO1)
What are the assumptions made when using the the mark-release-recapture method to make valid estimates of population size?
1. The population size does not change between the two capture times.
* There should be no increase in predation of the marked organism
* There should be no migration
2. The marked organisms have enough time to (randomly) disperse/distribute into the rest of the population
3. The marking should not rub off or be lost
4. Sample population is large enough
Populations in ecosystems (AO1)
Mark, release, recapture equation
You must be able to recall and apply this equation
Populations in ecosystems (AO1)
Anolis sagrei is a species of lizard that is found on some of the smallest Caribbean islands.
Describe how you could use the mark-release-recapture method to estimate the number of Anolis sagrei on one of these islands (3 marks).
1. Capture sample, mark and release;
2. Method of marking does not make it more visible to predators (i.e. does not affect survivial the lizards);
3. Leave sufficient time for lizards to (randomly) distribute (on island) before collecting a second sample;
4. (Population =) number in first sample × number in second sample divided by number of marked lizards in second sample / number recaptured.
Populations in ecosystems (AO2)
20
Populations in ecosystems (AO2)
The scientists used the mark-release-recapture method to determine the number of pine martens in one area of forest. They captured, marked and released a first sample of 25 pine martens. A week later, they captured a second sample of 35 pine martens from the same area of forest. The scientists calculated that there were 125 pine martens in that area of forest.
Using the information provided, calculate how many pine martens in the second sample were marked.
7 pine martens
Populations in ecosystems (AO2)
Blue tits are small birds that live in woods. An ecologist estimated the size of the blue tit population visiting gardens near a wood in November.
- She trapped 28 blue tits. She marked all of these birds with small metal rings on their legs.
- Two weeks later, she trapped another sample of blue tits. Of these birds, 18 were marked and 20 were not marked.
Use the data to estimate the size of the blue tit population.
59
Succession (AO1)
Hostile environments such as rock and sand are colonised by ______________
pioneer species
Succession (AO1)
Pioneer species example
Lichen
Succession (AO1)
TRUE or FALSE:
Lichen are microorganisms
TRUE
Lichen are a symbiotic association between a fungus and algae and/or cyanobacteria
Succession (AO1)
Characteristics of pioneer species
Photosynthesise;
Fix nitrogen;
Asexual reproduction;
Tolerance to hostile environments;
Succession (AO1)
At each stage in [1], certain species may be recognised which change the [2] so that it becomes more suitable for other species with different adaptations. The new [3] may change the environment in such a way that it becomes less suitable for the previous species.
[1] succession
[2] environment
[3] species
Succession (AO1)
Succession occurs in natural ecosystems.
Describe and explain how succession occurs (5 marks).
1. (Colonisation by) pioneer (species);
2. Change in environment / example of change caused by organisms present e.g. adds more humus;
(humus = is the formation of a thin / basic layer of soil)
3. Enables other species to colonise / survive;
4. Increase in biodiversity;
5. Stability increases / less hostile environment;
6. Climax community;
Succession (AO1)
Final stage of primary succession
Climax community
Succession (AO1)
Features of a climax community
1. Same species present (over long time) / stable community (over long time);
2. Abiotic factors (more or less) constant (over time)
3. Populations stable (around carrying capacity)
Succession (AO1)
What happens to the pioneer species as succession progresses to the next stage?
They are outcompeted;
by species better adapted to the less hostile environment;
(This is a form interspecific competition)
Succession (AO1)
The species that are present change during succession. Explain why (2 marks).
- Species / plants / animals change the environment / less hostile (habitat);
e.g. add humus / nutrients etc. - New species / plants that colonise this environment outcompete original species (e.g. pioneer species);
Succession (AO2)
Crabgrass
Succession (AO2)
1. Beach grass is the pioneer (species);
2. Pioneers/named species change the (abiotic) environment/habitat/conditions/factors;
Accept example of change e.g. more humus
3. (So) less hostile for named species OR
(So) more suitable for named species;
4. Conifer/hardwood trees represent climax community;
Succession (AO2)
Explain the advantage to a plant that colonises 50 years after the pioneer species of having a high rate of photosynthesis at low light intensities.
Plant will grow / survive in the shade / when overshadowed (by taller plants) / when receiving less light;
Note that taller trees are a key feature of a climax community
Succession (AO1)
Reasons for conserving rainforests
1. Conserve / protect
species / plants / animals / organisms
OR For (bio)diversity;
2. Conserve / protect habitats
OR Provides / many habitats ;
3. Reduces climate change;
4. Source of medicines/drugs/wood;
5. Reduces erosion/eutrophication;
6. (For) tourism;
Succession (AO2)
Explain why conservation of habitats frequently involves management of succession.
Prevents a climax community from forming;
Habitats in earlier stage ofsuccession may be better for some species;
E.g. ground nesting birds on heather moorland
Inheritance (AO1)
Phenotype
Expression of genetic constitution / genotype / allele(s);
AND its interaction with the environment;
Inheritance (AO1)
Dominant allele
Is always expressed / shown
in the phenotype;