Biology 1A - ecology Flashcards
what is population ecology
the study of factors affecting the size of a population and how it changes over time
what affects the size of a population and how it changes over time?
adding or removing individuals can affect population size and over time the population may
1. reach a stable size
2. fluctuate irregularly
3. rise and fall in regular cycles
what is the definition of a population
a group of individuals of a single species living in the same general area
how is a population described
- by their boundaries ( natural = lake, island etc. arbitrarily defined = country)
- by their size (number of individuals)
how do individuals in a population interact
- reproduce
- compete for resources
what is intra-specific competition
competition for resources between members of the same population/ species
what is inter-specific competition
competition for resource’s between members of different populations/ species
what are 3 important population concepts
- populations have structure
- populations are regulated
- populations are dynamic over time
describe the population pyramid (population structure)
it describes population age and structure
- births add individuals to the base of the pyramid only
- deaths remove individuals from the population at all ages after birth
describe the three types of age related survivorship (survivorship curves) (population structure)
1) mortality highest in older age classes, found in long lived species living in stable environment, iteroparous (reproduction spread throughout life time) eg gorillas
2) mortality constant throughout lifespan, found in short/ medium lived species, living in a relatively stable environment, iteroparous (reproduction spread throughout life time) eg squirrel
3) high mortality in juveniles, short lived species in unpredictable and temporary environments, often semelparous (reproduction in a single breeding event)
give an example of a species being intermediate to survivorship curves (population structure)
birds:
mortality often high in early life (type 3)
but fairly constant among adults (type 2)
what are the different spatial structures of populations? (population structure)
1) random = position of individuals is independent of other individuals, occurs in absence of strong competition or constant distribution of key physical and chemical factors
2) uniform = regular dispersion, planted crops, territorial animals
3) clumped = individuals aggregate in patches, aggregate in areas of high resource availability or favourable physical conditions, mating behaviour and group predation or defence against predators can also influence dispersion
what is the dispersion of s species shaped by (population structure)
the ecology of a species
what is population growth and the equation (regulation)
population growth = rate of change at each instant time
equation = dN/dt = rN
dN/dt = change in population size over short (instantaneous) time intervals
r = per capita change in population size N at each instant time
describe exponential population growth? (regulation)
occurs under ideal conditions, all individuals have access to abundant food and reproduce at physiological capacity
under such conditions, populations may increase in size by a constant proportion at each instant
describe the equation of exponential population growth (regulation)
dN/dt = rN
r is the intrinsic rate of increase, the per capita rate at which an exponentially growing population increases in size at each instant in time
(larger dN/dt value = steeper curve)
describe the logistic growth model (regulation)
the per capita rate of population growth approaches zero as the population size nears carrying capacity (K)
what is the equation for the logistic growth model (regulation)
starts with exponential model and adds an expression that reduces per capita rate of population growth as population size (N) increases
dN/dt = rN (K-N)/K
what shape is the curve for logistic growth (regulation)
s shape
what factors affect density dependant regulation in the wild? (regulation)
- competition for resources
- territoriality
- disease
- intrinsic factors
- toxic wastes
what are density independent factors (regulation)
factors that limit the size of a population without being affected by the population’s size. They can include:
- Weather and climate
- natural disasters
- pollution
- oxygen availability
what is our current understanding of population regulation
- both density dependant and density independent factors can operate
- regulation differs between species
- in some species both have been shown to operate
- must be some density dependant element or population will become extinct
what is population dynamics
focuses on the complex interactions between biotic and abiotic factors that cause variation in population size
describe population dynamics peak
1) population increases due to ideal conditions
2) interspecific competition occurs at peak
3) steep decrease due to factors such as food limitation, diseases, predation etc
4) peak followed by extended low
populations can go through dynamic cycles
why should we conserve nature
human activities threaten biology
ethical- moral reasons to save species
nature provides ecological services
what is conservation biology
integrates ecology, physiology, molecular biology, evolutionary biology and genetics in effort to conserve biological diversity
what are examples of some ecosystem services
cultural = recreation, tourism, spiritual and religious consequences
provisioning = food and drink, natural medicines, water supply, materials
regulating = clean air, flood management, disease and natural pest control, pollination
supporting = photosynthesis, nutrient recycling, space for wildlife
what are the three main levels of biodiversity
- genetic diversity
- species diversity
- ecosystem diversity
why is genetic diversity important
small population = inbreeding/ genetic drift = lower individual fitness and population adaptability = loss of genetic variability = lower reproduction and higher mortality = smaller population
what is species diversity?
the number of species in an ecosystem or across the biosphere
how many species are on earth
2.16 million named
estimated to be 5-10 million
where in the world has highest biodiversity
1) brazil amazon rainforest
2) central Africa and south east Asia
3) rest of the world
what are the three patters proposed to explain declining poleward biodiversity and higher tropical diversification rates
- “tropics as a cradle model” where origination rates are higher in tropical areas and distinction rate do not vary with latitude
- “tropics as a museum” model where origination rates are constant and extinction rates are lower in the tropics
- “out of the tropics model” where the origination rates are higher and extinction rates are lower in tropical areas
can species richness vary by altitude
yes
what are the stages on the international union for conservation of nature (IUCN) red list of threatened species
data deficient
least concern
near threatened
vulnerable (globally threatened)
endangered (globally threatened)
critically endangered (globally threatened)
extinct in the wild
extinct
how many species are threatened with extinction
more than 42,100 species
what are the 4 major threats to biodiversity
- habitat loss
- introduced species
- overharvesting
- global change
how do introduced species (invasive alien species) affect biodiversity
animals or plants introduced by humans
invasive alien species are a subset of alien species that have established and spread having negative impacts on nature and people
they cause these effects by
- changing ecosystems
- predation and herbivory
- competing with native species
how does habitat loss affect biodiversity
human alteration of habitat through agriculture, forestry, urban development, mining and population (greatest threat)
how does over harvesting affect biodiversity
harvesting of organisms that exceeds the ability of their populations to rebound
species with restricted habitats are especially vulnerable to over harvesting
what global changes reduce earths capacity to support life
climate: temp, drought, storms
atmospheric chemistry: ozone layer, air pollution
major ecosystem: rainforest, ocean acidity
how can we conserve biodiversity
find nature based solutions
increase protected areas
what is a biodiversity hotspot
a relatively small area with numerous endemic (found nowhere else) and many endangered and threatened species
how do we safeguard our UK protected Areas
- national legislation
- European union directives or other European initiatives implemented in UK legislation
- protected areas set up under global agreements Ramsar (wetland) sites
- marine protected areas
what are movement corridors
a way to conserve landscapes
- narrow strip or series of small clumps of habitat connecting otherwise isolated patches
- promote dispersal and reduce inbreeding
- in areas of heavy human use
what has lead to the decrease of water voles in Glasgow and what conservation efforts are planned
decrease:
Complex urban land-use
Redevelopment = loss of grassland
Mitigation
Relocation
Conservation Action Plan:
Habitat creation
Monitoring: water voles, mink and other predators
what factors affect the abundance and distribution of organisms
physical factors = temp, water, sunlight, wind, soil chemistry, disturbance etc
biotic factors = predator/ prey, parasites, symbionts, competitors
what are the levels of ecological organisation
- biosphere - parts of the earth inhabited by organisms
- biome - a climactic region eg. tundra, deep sea
- ecosystem - functional unit of ecology; the organisms in a habitat type that interact to create its structure
- community - a subset of the ecosystem that is found in one location
- population - members of one species that interact together in an area
- individual
what do different taxonomic groups show?
parallel patterns of biodiversity in distribution
(not the case for threatened species)
where are there commonly more species (patterns of biodiversity)
more near the equator than the poles
what are the most likely explanations for more species near the equator rather than the poles (global patterns in biodiversity)
greater climactic stability and productivity at equator, leading to greater speciation/ smaller niches
can be illustrated by plotting species richness at a location in relation to water availability - measure potential productivity
what factors impact how many species are in an area
water availability
temperature
area of habitat
emigration and extinction rates
describe theory of island biogeography (MacArthur & Wilson)
greater barriers to colonisation will result in lower diversity
so distance of “island” from main habitat mass should be important
describe immigration and extinction rates in relation to island biogeography theory
no of species can be explained by immigration and extinction rates
where lines on graph cross over is equilibrium
immigration and extinction rates depend on island size - result in different equilibrium biodiversity’s
compare immigration and extinction rates on small and large islands ( island biogeography theory)
small island = immigration will be LOWER and extinction will be HIGHER shifting equilibrium to the left
large island = immigration will be HIGHER and extinction will be LOWER shifting equilibrium right
compare immigration and extinction rates on near and far islands to the main habitat (island biogeography theory)
far = immigration will be LOWER and extinction will be HIGHER shifting the equilibrium left
near = immigration will be HIGHER and extinction will be LOWER shifting equilibrium right
describe Bergmann’s rule
in birds and mammals find larger bodies at higher latitudes
describe Allen’s rule
find shorter appendages at higher latitudes
what is the explanation for Bergman’s and Allen’s rule
Mammals and birds need to conserve heat towards the poles, but lose heat near the equator
where is body size larger
in regions of lower biodiversity
what do all organisms need and how do they get it
energy :
1) either from the sun converted to organic molecules by primary producers (photosynthesis)
2) chemicals
3) from each other
what is gross primary production (GPP)
the total amount of energy generated by autotrophs in an ecosystem
autotroph = an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. produce energy but also use it up themselves
what is net primary productivity (NPP)
a measure of how much of the gross primary production is available to other organisms
NPP = GPP - respiration by autotrophs
NPP usually about half of GPP
what is NPP greatest?
in regions with greatest rainfall
(brazil, central Africa, south east Asia)
what can limit NPP
rate of NPP constrained by:
- energy (temp, light penetration of aquatic ecosystems)
- water (for terrestrial ecosystems)
- limiting nutrients - usually nitrogen and phosphorus
what are the trophic levels (food chain)
1) plants (primary producers) eaten by
2) herbivores (primary consumers) eaten by
3) carnivores (secondary consumers) eaten by
4) top carnivores (tertiary consumers) eaten by nothing
what are trophic levels
hierarchical levels in an ecosystem, consisting of organisms sharing the same function in the food chain and the same nutritional relationship to the primary sources of energy
Collectively form an ecosystem made up of different functional groups
what is lost at each step of the food chain (each trophic level) and what does this cause
energy is lost at each level
causes pyramid of biomass/numbers
so, biomass of plants greater than that of herbivores, greater than that of carnivores etc. (top predators more rare)
what are the two ways ecosystems are driven (trophic levels)
input at the bottom of the food chain : increasing energy or nutrient supply will increase populations at all levels
pressure from predators (“trophic cascade” control): herbivore numbers limited by predators not primary production, adding a top carnivore increases herbivores
what is a food web
a diagram that shows the feeding relationships between species in an ecosystem
what are dominant species (trophic levels and food chains)
the most common/ have biggest biomass so have a big effect on ecosystem/ food web
what are keystone species (trophic levels and food chains)
species not necessarily numerous but have pivotal role because of their niche
eg. sea star Pisaster feeds on muscles so creates gaps for other species
can act as a control
eg. beavers create new niches
what can removal of keystone (control) species lead to
can lead to reduction of biodiversity as dominant species can overpower everything else
what is bioaccumulation
increasing concentrations of pollutants and other non-metabolised molecules up the food chain
eg DDT, PCBs, methyl mercury
who was Rachel Carson 1907-1964
published book “silent spring” on the effect of agrochemicals
resulted in a ban of DDT in USA and other parts of the worlds
raised global awareness of the dangers of contaminants in ecosystems
was the founder of environmental movement
what was the effect of bioaccumulation of DDT
caused egg shell thinning in birds at end of food chains due to higher DDT concentrations
wiped out predator populations
(birds of prey, pelicans, seabirds)
what types of animals can be subject to bioaccumulation
detritivores and scavengers
eg vulture population decline
what led to the critical endangerment of species of vulture in Asia and what was the negative effects of this?
bioaccumulation of diclofenac medicine given to humans and cattle to prevent inflammation since 1990s
no banned and captive breeding program set up too try recover populations
negative effects: no longer removing carcases, increase in feral dogs/rabies, parsis leave human dead for vultures, no cant causing controversy
what is the negative effects of neonicotinoids?
insecticide has a persistent lethal effect of bees
why does competition arise in ecosystems (biotic interactions)
because of recourse limitations
what is the competitive exclusion principle (biotic interactions)
states that if two species compete for exactly the same resource, one will drive the other to (local) extinction
what is an ecological niche (biotic interactions)
the position of a species within the ecosystem
what are the two types of niche (biotic interactions)
fundamental niche = niche potentially occupied by a species
realised niche = niche actually occupied by that species
what causes the difference between fundamental and realised niches (biotic interactions)
due to competition
the presence of a species may limit the realised niche of another species
give an example of character displacement (biotic interactions)
eq. common spiny mouse and golden spiny moth both living in desserts in middle east
they coexist (sympatry) common mouse is nocturnal and golden mouse is diurnal
when living separately they are both nocturnal
experiment removal of common mouse golden ones shift to become nocturnal
adapt to avoid competition
what is character displacement (biotic interactions)
- a tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species
-results in reduced competition
how do predators shape behaviour of prey (biotic interactions)
as predator evolve better capture method prey evolve better method of evasion (evolutionary arms race)
(can show parallel cycles)
give an example of the evolutionary arms race (biotic interactions)
1) moths fly at night to avoid predatory birds
2) bats evolve echolocation to fly at night and feed on moths
3) moths can listen for bats echolocation clicks and either fly erratically, respond with own licks of drop out of sky
4) some bats produce only quite clicks when approaching moths
5) some moths can tell the difference between searching clocks and fast clicks of a bat homing in and only react to fast ones
6) some bats produce noise to jam echolocation of other nearby bats, reducing their moth capture rates
can can parasitism affect behaviour of prey? (biotic interactions)
host changes behaviour to avoid parasite
less commonly parasite causes change in behaviour of host to increase fitness of parasite
what is commensalism (biotic interactions)
parasite host relationship where one species benefits and other if neither harmed or helped
rare -usually affects both species
what is mutualism (biotic interactions)
parasite host relationship where both benefit from association
can be optional (facultative) or can have developed into essential relationship (obligate) where at least one cannot survive without the other
