The Living Environment (A2); Life Processes In The Biosphere (Complete) Flashcards
What must organisms be adapted to in their habitat in order to survive?
The range of abiotic and biotic conditions existing
How do species become better adapted and evolve?
Through processes that involve the production of new characteristics by random mutations, followed by natural selection, which gives an increased chance of survival to better adapted individuals
When may poorly adapted organisms die?
If the environmental factors are unsuitable or if other species are better adapted
What does the range of tolerance within which organisms can survive mean?
For any specific condition/factor most organisms survive within a relatively narrow range
Why is a population with a large gene pool more likely to survive environmental changes and why is this an advantage?
-Some individuals will be adapted to new conditions
-Even though the non-adapted would die, the survivors would be able to breed & rebuild the population as their offspring will be adapted to surviving the new conditions
Why is the understanding of a species’ adaptations important?
-Helps in understanding its habitat requirements which is important during decision-making in planning conservation management
-Helps when deciding how to manage the environment & how to provide conditions that increase the chances of survival
What kind of decisions are made to an environment when talking into account a species’ adaptation?
Often involve small beneficial changes to a specific condition, where a species was close to one extreme of its range of tolerance & where changing conditions threatened to make the conditions unsuitable for survival
What is the survival and distribution of species mainly controlled by?
Abiotic factors
What are the important abiotic factors that affect species distribution?
-Light
-pH
-Water
-Mineral nutrients
What must the abiotic conditions also be if they are within the tolerance range of a species?
Must be adapted to the inter-species relationships involved with biotic factors
What are the important biotic factors that affect species distribution?
-Food supply
-Pollination
-Disease
-Seed dispersal
What stage do all species have in their life cycle and why?
-When movement to colonise new habitats can take place
-Essential to avoid extinction as changing conditions make current location unsuitable for survival
What happens when a species colonises an area?
It will change the habitat, which may make it suitable for other species to colonise that couldn’t have survived there before
Where can the range of processes which happen after species colonise an area be seen?
Newly created habitat which currently have no life, eg a new pond, bare rock exposed by a retreating ice sheet, landslide or created by a volcanic eruption
What are the stages in the sequence of events that follows a species colonising an area and what are they named after?
Seres: each has a prefix named after the starting conditions;
-Water; hydrosere
-Bare rock; lithosere
-Sand; psammosere
What is the process of changes in a sere called?
Ecological succession
What are the stages involved in ecological succession?
-First living organisms to colonise (‘pioneer species’) must be adapted to abiotic conditions which are more extreme than later on when the habitat will support a higher biomass, eg less shelter from strong winds/more extreme temps
-As time passes & populations increase, pioneer species change the habitat & make it suitable for species that weren’t able to survive before. New colonisers may out-compete pioneer species which become less dominant & may eventually die out
-New colonisers also change conditions, making habitat suitable for colonisation by more species
-As changing abiotic conditions become ↓ extreme adaptations needed for survival are increasingly based on biotic factors & inter-species relationships
-Sequence of new species colonising, thriving, then dying out continues until final community of species develops which remains dominant as long as climate doesn’t change (this is the climax community). Species that make up community are controlled by the climate, so it’s often called the climatic climax community
What are critical determinants of a biome and examples of how this happens?
-Rainfall & temperature
-Eg, areas which have water available throughout year typically develop into woodland. Type of woodland developed is controlled by temperature; tropical rainforests develop at higher temps, temperate deciduous woodland at moderate temps & boreal conifer forest in cooler environments
-Areas where rainfall varies season to season usually become grassland, eg tropical savannah + temperate grassland
Ecological succession; what is the first stage in a hydrosere?
-When an area of freshwater is created it’s usually quickly colonised by single-celled algae from soil
-Birds, eg herons + ducks & flying insects, eg water beetles + pond skaters, can bring in spores, seeds of algae, diatoms, & plants
-Lake edges start to be colonised by rooting plants eg reeds, lilies, & reedmace
-However, open water may be too deep for such plants so only floating plants live there
-The more the area is colonised by plants, the more food & shelter there is so more animals that arrive can survive
Ecological succession; what is the second stage in a hydrosere?
-As plants grow & die, lake gradually fills in w/ dead organic matter + soil and sediments carried in from the surrounding area
-As water becomes shallower, conditions continually change until rooted plants can survive
-Emergent plants, that have their leaves above the water, shade the submerged plants which gradually die out
Ecological succession; what is the third stage in a hydrosere?
-As sediments fill the lake & open water recedes, aquatic species progressively disappear
-As soil accumulates & develops to the extent that it can support the weight of much bigger plants, trees that can survive in waterlogged soil, eg willow and alder, start to colonise the area
Ecological succession; what is the fourth stage in a hydrosere?
-As transpiration by trees removes water & more sediments accumulate the soil becomes drier
-Trees like oak will be able to colonise
-These larger trees create a denser canopy, providing shade which inhibits the growth of smaller plants
Ecological succession; what is the last stage in a hydrosere?
-Eventually, the community is dominated by the largest trees, w/ other plants & animals living in, on, or under them
-Few of the original species involved in the early stages of the ecosystem’s development are still present
Ecological succession; what is a lithosere caused by?
A cliff fall, the retreat of a glacier, or a volcanic eruption
Ecological succession; what are the initial abiotic conditions before a lithosere is created like?
-Very harsh & unsuitable for most organisms
-Temperatures are extreme, water availability is severely limited & there is no soil
Ecological succession; what is the first stage in a lithosere?
-Simple autotrophs eg lichens & algae are the first to colonise the area
-Conditions improve as dead organic matter & rock fragments gradually accumulate
-Mosses colonise & thin layer of soil starts to build up
-Grasses and ferns then colonise
Ecological succession; what is the second stage in a lithosere?
-As the layers of soil form & plants get larger, the abiotic factors become less extreme
-The conditions are never as hot/cold, or wet/dry, as they were at the beginning of the community’s development & the development of the soil makes plant nutrients more available
-Seedlings of less hardy plants can survive under the shade of larger plants
-Once pollinating insects become established flowering plants colonise & survive as pollination takes place
Ecological succession; what is the last stage in a lithosere?
-Once the soil is deep enough & the edaphic factors (soil factors) are suitable, trees can colonise
-The first tree species to establish usually have wind-blown seeds, eg birch trees, while the seeds of later species are dispersed by animals, eg beech & oak trees
Ecological succession; why are the early stages in a hydrosere and lithosere so different and how are these changes reduced?
-Due to their different original conditions
-As succession occurs these differences are reduced & final communities are very similar to each other as they are controlled by the climate of the region which is the same for both communities
Ecological succession; what are the stages in a psammosere?
-Plant nutrients aren’t readily available, drainage is rapid so water supplies are poor & moving sand makes it difficult for plants to establish a good root hold w/out being covered + killed
-As plants succeed in colonising, sand is stabilised, nutrient supplies
increase, organic matter builds up, & water becomes more available
-Eventually, the sequence of changes in the community of species will establish the same climatic community that would have been produced by a hydrosere or lithosere
What are plagioclimax communities and what do they involve?
-In many areas, human activity that deflects the climax community occurs regularly, so natural climax community doesn’t have time to reform & new community of species develops; a a plagioclimax
-A long-term balance betw succession & human activities that maintain many plagioclimax communities produce habitats that don’t appear to change, eg grassland, lowland heathland & moorland
What does the conservation of climax and plagioclimax communities involve?
-Conservation of climax communities eg natural rainforest, coral reefs, mangroves & Antarctica typically takes the approach of minimal human impact
-However, in the UK, conservation management of plagioclimax communities is usually through maintenance of the traditional activities that created them
What is secondary succession and why is it quicker than primary succession?
-Human activities that disturb climax communities, eg tree felling, ploughing, & burning, recreate conditions that were suitable for species that colonised the area earlier in sequence of ecological succession
-These species recolonise the area. If the habitat is left alone, succession will continue to change, will eventually re-create climax community; secondary succession
-This takes place more rapidly than primary succession as soil doesn’t have to develop & many of the seeds will already be present so there are fewer delays caused by time taken for species to colonise
Species diversity & ecological stability; in what kind of environments is species diversity low and how is this impactful?
-In extreme environments dominated by abiotic factors & where populations are likely to fluctuate dramatically, species diversity is often low
-Where few food species are available, a change in availability of one food species will have a big impact on the number of predators
-This will then impact the availability of the food species, creating cycles of population rise and fall
Species diversity & ecological stability; in what kind of environments is species diversity high and how is this impactful?
-Less abiotically extreme environments usually have higher biodiversity
-These become more stable ecosystems in which populations are dominated by biotic factors. Examples include tropical rainforests and coral reefs
Species diversity & ecological stability; what is the formula for Simpson’s Diversity Index Formula and what does it show?
-D = N(N-1)/ sum of n(n-1)
-N= total number of organisms (all species)
-n= total number of organisms of an individual species
-Higher value of D= higher biodiversity
Species diversity & ecological stability; how can the total number of species be estimated and why is this difficult?
-As we have not yet discovered all the diff species that exist it’s not easy to estimate how many there are
-However, the past rate of discovery can be used as the basis for estimating the number
-The gradual reduction in the rate of finding new species can be used to estimate the total number of species that have not yet been discovered, therefore the total number of species that exist
-New species are currently being discovered at a rate of about 20,000 per year
-Current estimates for the total number of species vary from 5-100 m
-Only 2m species have so far been named
Species diversity & ecological stability; what does population dynamics involve?
The processes that can cause populations to change in size & structure
Species diversity & ecological stability; what is the number of species living in an area controlled by?
The balance of factors which tend to increase or reduce the population
Species diversity & ecological stability; what is the advantage of successful wildlife conservation on population dynamics?
Will maximise the factors that increase the population while minimising the factors that reduce it
Species diversity & ecological stability; what can the environmental factors that affect the death rate be controlled by?
Good environmental management
Species diversity & ecological stability- population dynamics/regulation; what factors determine birth rate?
-Maximum birth rate (natality rate) is determined by the natural ability of the species to reproduce
-Evolution has produced birth rates for each species that are appropriate for the death rate
-Species w/ lower chances of survival have higher birth rates
Species diversity & ecological stability- population dynamics/regulation; what factors determine death rate?
Disease, drought, predation, food shortage
Species diversity & ecological stability- population dynamics/regulation; what are r-selected species and their role + examples?
-Species that can respond rapidly to low survival rates
-Reach sexual maturity quickly, produce many young & can disperse widely
-Eg mice, locusts, greenfly
Species diversity & ecological stability- population dynamics/regulation; what are k-selected species and their role + examples?
-Species that recover slowly from a decline in population
-Usually reach sexual maturity at an older age, produce few young but often live for a long time
-Increase in death rate caused by a change in habitat/by human exploitation may cause population crash
-Low reproduction rate of k-selected species may make it impossible to replace losses
-Eg whales, elephants, rhinos
Species diversity & ecological stability- population dynamics/regulation; why is an understanding of population dynamics important?
To monitor the survival of a species, breeding success & to assess Maximum Sustainable Field (MSY); estimate of greatest exploitation possible w/out causing unsustainable long-term population decline
Species diversity & ecological stability- population dynamics/regulation; which factors are required to forecast a change in the size of the population?
-Current population
-Number of births & deaths
-Number of individuals immigrating & emigrating
Species diversity & ecological stability- population dynamics/regulation; how do you calculate population?
Starting population + births + immigrants - deaths - emigrants
Species diversity & ecological stability- population dynamics/regulation; what are density independent factors and how do they affect mortality rates?
Factors where the population density has no effect on chances of survival of an individual, eg drought, food, volcanic eruption
Species diversity & ecological stability- population dynamics/regulation; what are density dependent factors and how do they affect mortality rates?
-Include factors where chances of an individual surviving depend on the population density of the species
-Survival chances are usually higher when the population density is low & lower when population density is high
-Eg; food supply: intra-species competition for food, disease spreading more easily
Species diversity & ecological stability- population dynamics/regulation; what is carrying capacity and how can it impact mortality rate?
-Greatest population an area can support indefinitely w/out damaging/over-exploiting environment
-Mortality rate in a population changes if population size is above/below carrying capacity so that population size changes back to carrying capacity
Species diversity & ecological stability- population dynamics/regulation; how is the predator-prey population relationship closely related?
-When prey population rises there’s a lot of food for predators, so their population rises → high predator population causes prey population to decline
-Low prey population creates a food shortage for the predators so their population declines → low predator population allows prey population to rise again
Species diversity & ecological stability- population dynamics/regulation; why may intervention to artificially control the population through culling be required?
To enable the species/habitats to survive where natural control mechanisms no longer regulate the population
Species diversity & ecological stability- population dynamics/regulation; when may intervention to artificially control the population through culling be necessary?
-Breeding rate of endangered species is low, so captive breeding & release programme is needed to maintain/ increase population
-Non-indigenous species is introduced which reduces populations of indigenous species as it’s a predator, competitor or pathogen
-Indigenous predator has been removed so its prey species becomes over-populated & needs to be culled to avoid ecological damage it may cause by its impact on other species. Eg, as wolves in Scotland have been exterminated their prey species, Red Deer, must be culled to prevent population rising too high which would lead to over-grazing
Ecological terminology; what is taxonomy and a taxon?
-Science of grouping organisms according to the similarities in their features
-Any taxonomic group; taxon
Ecological terminology; why is the grouping of organisms into most taxa subjective?
-Opinions can change as new information becomes available
-Eg African elephant is now considered to be 2 distinct species; African Bush Elephant (Loxodonta africana) & African Forest Elephant (Loxodonta cyclotis)
-Species is the only ‘real’ taxa, although our understanding isn’t always good enough to accurately distinguish betw very closely related species
Ecological terminology; what is a species and what do organisms do within one?
Group of closely related organisms that resemble each other more than members of other groups
Form reproductively isolated group that naturally breed w/ each other to make fertile offspring
Ecological terminology; why can most species not produce fertile offspring with other species?
-Differences in behaviour would prevent individuals from attempting to mate
-Anatomical differences make mating impossible
-Even if mating was possible, differences in numbers/shape of chromosomes may make fertilisation/cell division impossible
Ecological terminology; when may very closely related species be capable of producing fertile off spring?
In captivity where they aren’t isolated & natural behavioural patterns break down, they may mate & produce fertile offspring, eg some duck species
Ecological terminology; what are the ways in which species are named?
-Species are given Latin names which are used by ecologists in all countries to avoid confusion
-First part of species name relates to the genus; a group of the most closely related species, eg Passer; 20 closely related sparrow species
-Second part of the name is added to identify an individual species within the genus, eg Passer domesticus; House Sparrow of Europe, Asia, N Africa
-Common names of all taxa have lower case letters but some authorities use upper case letters for specific species. Eg rhinoceros; several species, Black Rhinoceros is a species
Ecological terminology; what is evolution and what is it driven by?
-Process that changes the gene pool of a species, in some cases separating gene pools which eventually become 2/more species
-Driven by increased chance of survival, produced by being better adapted to local conditions than other species members. Characteristics providing survival advantage can vary in different areas
-Over time may produce isolated populations that are sufficiently different from other populations so no longer interbreed; are closely related but different species
Ecological terminology; what is a habitat + examples?
-An area/location where a species/community of species lives
-Eg, moles in the soil within a grassland or Blue Tits living in foliage of trees in a woodland
Ecological terminology; what is an ecological niche and why is it unique to each species?
-Role a species plays in its habitat; includes way it uses environmental resources & its relationship to other species, eg pollination/seed dispersal
-Eg the tawny owl is a nocturnal carnivore, nesting in holes in hollow trees, feeding on small mammals & birds
-Two species can’t occupy exactly the same niche within a single habitat as one would be better adapted than the other; less well adapted wouldn’t be able to compete & would die out
Ecological terminology; what is a population + examples?
Includes all individuals of a single species that live in a particular area, eg all English Oak trees in a deciduous woodland/all Common Carp in a lake
Ecological terminology; what is a community of species + example?
Includes all members of all species that live in an area, eg combination of all populations of all species in an area such as all species of plants, bacteria, fungi, Protista, archaea, animals
Ecological terminology; what is an ecosystem + examples?
-Combination of biotic & abiotic features of an area
-Includes community of species, their inter-relations w/ each other & their relationship w/ the physical environment eg energy, water & nutrients
-Are usually relatively self-contained w/ few movements of organisms in/out of the ecosystem
-Eg include tropical rainforest, estuary, savannah grassland, coral reef
Ecological terminology; what is a biome and what is its distribution controlled by?
-Large geographical region w/ specific climatic conditions within which a characteristic community of species lives
-Includes all areas where community is found, eg tropical rainforests, mangroves, savannah grasslands, tundra
-Usually named after the most obvious organisms, often the characteristic vegetation
-Distribution controlled by climatic factors, eg temperature, light levels, water availability, seasonal fluctuations
Ecological terminology; how are ecosystems and biomes distinguished from each other?
-Biome includes all areas covered by same community of species, eg tropical rainforests/all tropical coral reefs
-Ecosystems often have the same names as biomes but each isolated area is a different ecosystem, eg separate tropical coral reefs
-All coral reef ecosystems belong to the same coral reef biome & all tropical rainforest ecosystems belong to the same tropical rainforest biome
Ecological terminology; what is a biosphere?
All of planet Earth that’s inhabited by living organisms including land surface, soil, water, atmosphere
