biology option C1

species and communities

ecosystems

• a community and its abiotic factors

• individuals within a population interact with individuals of the same species (intraspecific) and of different species (interspecific)

• those interactions form a community that lives within a particular area

• non-living (abiotic) elements also shape a community

complex ecosystem

• variety of species and their feeding habits provides stability

• unique combination of populations and its abiotic environment

human activity

• negatively impacting ecosystems through the removal of vulnerable populations and species extinction

  • leads to simplified and unstable ecosystems

emergent properties

• arise from interaction of component parts: the whole is greater than the sum of its parts

limiting factors

• factors that limit the distribution of a species

• any factor that puts an upper limit on the size of a population

• can control growth, abundance and distribution of a population of an organism in an ecosystem

species within a community

• each species has an ideal range of environmental conditions in which they thrive

• distribution of a species is limited by these conditions, as organisms can’t tolerate too much variation from their ideal environment

• outer limits: zone of intolerance

polar bears

• distribution in arctic is connected to features that evolved over time

• can withstand air temperatures of -37ºC due to fur

• do not need to drink water, since they get water from chemical reaction that breaks down fat

• breed on sea ice and dig dens in show drifts

• territory: depends on the breakup and freezing of sea ice, and ability for them to access food supply (seals)

• have territories the size of Italy

transect

• a line across a habitat or part of a habitat which is used to explore a relationship between the population of organisms present and one or more abiotic factors

• used as a method of sampling, where they look at a sample from the population instead of counting each organism

• help determine the zone of tolerance of a species, by observing where there are lots or little organisms in relation to abiotic factors

• commonly carried out in

  • point sampling

  • continuous belt transect

  • interrupted belt transect

point sampling

• when points are marked at regular intervals along transect and data is gathered only at those points

• provides basic representation of abiotic or biotic factors, but may be light on data

• drawback: intervening data between points is missed

• sampling must reflect environment that it is happening in, so you must decide how far apart the points will be, to be the most reliable

continuous belt transect

• made of ‘belt’ of squares (quadrats) that lie next to each other in a row

• each quadrant is usually a 1×1 meter and is analysed for biotic or abiotic data

interrupted belt transect

• combination of point and continuous belt transect

• allows areas along transect to be studied, providing less data but is more representative of a gradient

modelling

• represents simplified version of reality

• can be used to

  • understand how an object, system or concept works

  • predict how it will respond to change

• analytical model: based on maths equations

• diagrammatic: used to show how different components of an ecosystem interact together, eg

  • nutrient cycle: carbon cycle

modelling drawbacks

• rely on expertise to make them

• can be interpreted differently

• may be inaccurate

• different models may show different effects with the same data

ecological niche

• the sum total of a species’ use of biotic and abiotic resources in its environment

• within a community, every species has a unique and important role to play in contributing to the environment in which it lives

  • spacial habitat: where the species lives in the ecosystem

  • nutrition: how a species obtains food; its feeding activities

  • relationships: interaction with other species in the ecosystem

fundamental niche

• broadest possible niche a species live in within its range, with no external pressure; idea of this is theoretical

realised niche

• actual mode of existence in which the species is really found, taking into account its limiting factors and interactions with other species

• always smaller than fundamental niche

competitive exclusion

• when two species occupy fully overlapping niches, the one with greater selective advantage will out-compete the other, leading to its extinction from that environment

• slight reproductive advantage will lead to extinction of inferior competitor

Georgi Frantsevich

• conducted landmark experiment which showed that no two species with the same habitat and completely overlapping niches can coexist

• two species of paramecium that were cultured separately and thrived, levelling off at max population frequency (carrying capacity)

• when cultured together, one was driven to extinction

competition

• interaction between organisms in which both are harmed

• arises when individuals depend on the same resource

herbivory

• interaction between primary consumer and producer

• primary consumers eat plants; predators of plants

• may be beneficial or harmful for the plant

• colorado beetle feeds of leaves of potato plants and causes crop failure

predation

• interaction between two living organisms where one catches, kills and eats the other

• tapeworm attaches to inside of cow or human intestines and eats partially digested food, depriving host of nutrients

mutualism

• interaction of two species where both benefit

• green algae and cyanobacteria

  • fungus benefits from sugars and organic molecules

  • algae benefits by being protected by filaments

parasitism

• interaction of two species where parasite feeds on and derives benefit from host which consequently suffers

commensalism

• interaction between two organisms where one benefits and the other neither benefits nor is harmed

• remora fish and sharks

  • remora attach to sharks to get a lift, and are protected from predators

intraspecific

• organisms compete with others of the same species for food or a mate

• intraspecific = same

interspecific

• when individuals of one species compete with those of another species

• interspecific = different

predator and prey

• predator: organism that feeds on another living species

• prey: the living species eaten by predator

• predator-prey relationship

  • lots of prey = increase in predators

symbiotic relationships

• commensalism

• mutualism

• parasitism

• interspecific: corals and microscopic unicellular algae (zooxanthellae)

  • coral provides protection and necessary compounds for photosynthesis

  • algae produce oxygen, excess products of photosynthesis, and remove metabolic waste of coral

  • byproduct: colours from pigments (gold-yellow to brown)

keystone species

• species that exerts a strong control on community structure without being abundant in number

• removal of keystone leads to collapse of the arch

keystone species examples

• sea otter

• elephants

• parrotfish