Biology Module 4

define populations, communities, ecosystems

• population: individuals of same species in a given area

• community: population + population of other species

• ecosystem: community + abiotic environment

what does size & health of environment indicate?

ecosystem’s condition

• decline in population = change in ecosystem

what is impacted by seasonal changes?

• seasons in northerm hemisphere (e.g. NA, Europe) are unpredictable, winter = harsh, spring = new organism growth

  • rapid increase each Spring breeding season

  • population declines each year due to predators, disease, old age

  • many die in winter every year

what do plants produce & why is it an issue? give an example

allelochemicals

• released by plants & concentrate in soil

• inhibit growth of other plants in the area & give the plant competitive advantage

• e.g. eucalyptus & casuarinas show allelopathy → produce chemicals that inhibit growht & development of neighbouring plants

define predator & what they impact

• organism which kills & eats another organism (prey) for sustenance

• affects abundance of prey; prey needs to reproduce as fast as it is predated upon to maintain constant population size

give examples of how interspecies interaction limits population size

• prey population size depends on food availability

• high predator population causes prey numbers to drop

• low prey population suppresses predator numbers

label the food pyramid & give examples

how do food chains transfer energy?

• when animal eats plant, it uses energy stored in plant to form its own body cells

• most energy lost in conversion from plant tissue to animal tissue

  • 10% moves to next trophic level

  • 90% lost via metabolism & waste

what are the 2 main subcategories for competition?

• intraspecies: between members of same species

• interspecies: between members of different species

what do plants compete for?

• water: keep tissue rigid & supported, photosynthesis

• light: for photosynthesis; make food using energy from sun

• minerals & nutrients from soil: for plants to make chemical needed in cells

• space: plants shed seeds far away so parent plant is not in competition with offspring

what do animals compete for?

• resources (food & water)

• mates

• habitat

• space & shelter (e.g. nesting sites)

what happens if an organism dies in competition?

move areas, adopt new strategies, become extinct/die

define symbiotic relationships

type of interaction where different species live together in close association

what are the 3 basic modes of symbiosis? give examples

• parasitism (+ -): trophic relationship where parasite feeds on host’s tissue or food in host’s gut, parasite benefits but host may be harmed (e.g. ticks, fleas on rats)

• mutualism (+ +): relationship occurs when 2 different species derive some benefit from coexisting together, neither can live without the other (e.g. sea anemones & clownfish → clownfish lures fish toward anemone & eats dead tentacles, keeping anemone & area around it clean while anemone’s poisonous tentacles provide protection from predator)

• commensalism (+ 0): relationship where one organism benefits & other is neither benefited nor harmed (e.g. sharks & remora)

define ecological niche & what it encompasses

• organism’s role within its ecosystem

• encompasses its food source, habitat, physiology, behaviour

what happens when two species in the same ecosystem overlap niches?

results in interspecific competition

what does the competitive exclusion principle state?

• two species cannot have identical niches in an ecosystem

  • competing species may coexist but cannot do so in a stable manner, eventually resulting in one species becoming locally extinct or adapting itself to different ecological niche

what do endangered species become threatened from? give an example

• from inability to adapt to different ecological niches when competition arises

• e.g. Australian koala (phascolarctos cinereus)

  • only east foliage from few eucalyptus trees

  • locally specific in diet (e.g. koalas in NSW forage on different eucalypts than koalas in Victoria)

  • ecosystems can only support limited number of koalas due to dietary preferences; thus species comes under threat when ecosystem becomes unbalanced (e.g. eucalypt forests cleared for development → koalas have fewer eucalypt trees → trees/koalas perish)

are populations dynamic & why do they respond to variation in environment?

dynamic & respond to variations in environment because it is influenced by abotioc & biotic factors

what are populations measured in?

• size: number of individuals in population

• density: number of individuals per unit area

• growth rate: change in number of individuals per unit time

when is population size & distribution in space & time apparent?

when each population measurement is known