Ecosystems & Ecology

species

species

a group of organisms sharing common characteristics that interbreed and produce fertile offspring

habitat

the environment which a species normally lives

niche

the particular set of abiotic and biotic conditions and resources to which an organism or population responds

fundemental niche

the full range of conditions and resources in which a species could survive and reproduce

realised niche

the actual conditions and resources which a species exists due to biotic interactions

abiotic factors

the non-living, physical factors that influence the organisms and ecosystem, ex: temperature, sunlight, pH, salinty, percipitation

biotic factors

the interactions between the organisms, ex: predation, herbivory, parastism, mutualism, disease, competition

interactions

the influences each species has on the population dynamics of others, and upon the carrying capacity of the others’ environment

population

a group of organisms of the same species living in the same area at the same time which are capable of interbreeding

limiting factors

slow population growth as it approaches the carrying capacity of the system

ecosystem

a community and the physical environment it interacts with; made up of the organisms, physical environment and the interactions between the living and non-living components within them

What are the two parts that compose the scientific names for species?

Genus name and species name

How are the scientific names for species written?

Always underlined or in italics with the genus name first with a capital letter

population density

average number of individuals in a stated area

3 factors affecting population size

natality, mortalirty and migration

natality

birth rate

mortality

death rate

what are some biotic factors included in an organism’s niche?

every relationship that organism may have, where it lives, how it responds to resources available, to predators, to competitors

what are some abiotic factors included in an organism’s niche?

how much space there is, availability of light, water etc.

carrying capacity

what does limiting factors do?

prevent a community, population or organism growing larger and slows down population growth as it approaches the carrying capacity of the system

what are two examples of limiting factors?

phosphate being in limited supply in most aquatic systems and low temperature in the tundra which freezes the soil and limits the water availability to plants

population dynamics

the study of the facotrs that cause changes to population sizes

what does all interactions result with?

one species having an effect on the population dynamics of the others and the carrying capacity of the others’ environment

competition

A common demand by two or more organisms upon a limited supply of a resource

intraspecific competition

competition between members of the same species

when does competition increase?

when population increases

what is an example of intraspecific competition?

deer: an individual or pair holds an area and fends off rivals, individuals that are the most successful reproductively will hold the biggest terriotry and hence have accesss to more resources and will be more successful at breeding

how do some species respond to intraspecific compeition?

by being territorial

competitive exclusion

one species totally out-competes the other

what is an example of competitive exclusion?

a garden that has become overrun by weeds, a number of weed species coexist together but often the original domestic plants have been totally excluded

what does competition reduce?

the carrying capacity for each of the competiting species, as both species use the same resource(s)

predation

when one animal, the predator, eats another animal, the prey

herbivory

an animal (herbivore) eating a green plant

parasitism

a relationship between two species in which one species (the parasite) lives in or on another (the host), gaining its food from it

mutualism

a relation between two or more species in which all benefit and none suffer

what are some forms of symbiosis?

mutualism, parasitism and commensalism

symbiosis

close and often long-term interaction between different biological species or species living together closely

commensalism

a relation between two or more species where one species benefits and the other is unaffected

what is one example of mutualism?

lichens, which is a close association of a fungu underneath and a green alga on top. the fungus benefits by obtaining sugars from the photosynthetic alga. the alga benefits from minerals and water that the fungus absorbs and passes onto the alga

what is another example of mutualism?

eguminous plants(beans, clover, vetch, peas etc.) and nitrogen-fixing bacteria — Rhizobium. the bacteria live inside root nodules in the legumes. they absorb nitrogen from the soil and make it available to the plant in the form of ammonium compounds. the plants in turn supply the bacteria with sugar from photosynthesis. this enables legumes to live on very poor soils.

exponential or geometric growth

a rapid, unbounded increase in population size due to abundant resources and minimal limiting factors

S and J curves

describe a generalised response of populations to a particular set of conditions (abiotic and biotic factors)

S curves

start with exponential growth. however, above a certain population size, the growth rate slows down gradually, finally resulting in a population of constant size.

environmental resistance

the area between the exponentional growth curve and the S-curve

J curves

starts with exponential growth and often overshoots before having diebacks.

diebacks

the sudden collpases in J curves

overshoot

when the population exceeds the carrying capacity on a long-term or continuing basis before the collapse occurs

what are the different phases of S stages?

lag phase, exponential phase, transitional phase and stationary phase

lag phase

the first stage of S curves, a period of time where the population size remains relatively small

exponential phase

the second stage of S curves, a period of time with rapid increase in population growth

transitional phase

the third stage of S curves, the period of time in between the exponential phase and the stationary phase

stationary phase

the fourth stage of S curves, when the population size stabilises since only a set number of organism can exploit the limited resources

community

a group of populations living and interacting with each other in a common habitat

what can both respiration and photosynthesis be described as?

processes with inputs, outputs and transformations of energy and matter

respiration

the conversion of organic matter into carbon dioxide and water in all living organisms, realising energy

what can aeorobic respiration be described as?

glucose + oxygen —> carbon dioxide + water

what happens during respiration?

large amounts of energy are dissipated as heat, increasing the entropy in the ecosystem while enabling the organisms to maintain relatively low entropy / high organisation also involves breaking down food, often in the form of glucose, to release energy which is used in the living processes

what does photosynthesis do?

convert light energy into chemical energy

what can photosynthesis be described as?

carbon dioxide + water —> glucose + oxygen

photosynthesis

the process by which green plants make their own food from water and carbon dioxide using energy from sunlight or the procces that produces the raw material for producing biomass

trophic level

the postion that an organism occupies in a food chain, or a group of organisms in a community that occupy the same postition in food chains

producer

also called autotroph, typically plants or algae and produce their own food using photosynthesis and form the first trophic level in a food chain

chemosynthetic organisms

a producer that produces food without sunlight, exception from the usual rule

ecological pyramids

quantitative models usually measured for a given area and time, include pyramids of numbers, biomass and productivity

bioaccumilation

the build up of persistent / non-biodegradable pollutants within an organism or trophic level because they cannot be broken down

biomagnification

the increase in concentration of persistent or non-biodegradable pollutants along a food chain

pyramids of biomass

contains the biomass (mass of each individual x the number of individuals) at each trophic level

pyramids of productivity

refer to the flow of energy through a trophic level, indicating the rate at which that stock / storage is being generated

what are the living processes?

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition

what is the equation for respiration?

C₆H₁₂O₆ + 6O₂ —> Energy + 6H₂O + 6CO₂

what is the equation for photosynthesis?

6CO₂ + 6H₂O —(light energy, chlorophyll)—> C₆H₁₂O₆ + 6O₂

compensation point

when all carbon dioxide that plants produce in respiration is used in photosynthesis, the rates of the two processes are equal and there is no net release of either oxygen or carbon dioxide. the plant is neither adding biomass nor using it up to stay alive at this point

when and why does a compensation point occur?

it usually occurs at dawn and dusk when light intensity is not too high

food chain

shows the flow of energy from one organism to the next

how is a food chain usually drawn?

showing the feeding relationships between species in an ecosystem with arrows connecting the species, usually by pointing towards the species that consumes the other (in the direction of transfer of biomass and energy)

consumers

also called heterotrophs, feed on autotrophs or other heterotrophs to obtain energy (herbivores, carnivores, omnivores, detritivores and decomposers)

which group is at the first trophic level and what is their source of energy?

primary producers, autotrophs: make their own food from solar energy, CO₂ and H₂O

what is the function of primary producers?

provide the energy requirements of all the other trophic levels, habitat for other organisms, supply nutrients to the soil, bind the soil / stop soil erosion

which group is at the second trophic level and what is their source of energy?

primary consumers, herbivores: consume primary producers

what is the function of primary consumers?

to keep consumers in check through negative feedback loops but also to disperse seeds

which group is at the third trophic level and what is their source of energy?

secondary consumers, Carnivores & Omnivores / Heterotrophs: consume herbivores and other carnivores, sometimes primary producers

what is the function of secondary and tertiary consumers?

pollinate flowers, remove old and diseased animals from the population

which group is at the fourth trophic level and what is their source of energy?

tertiary consumers, Carnivores & Omnivores / Heterotrophs: consume herbivores and other carnivores, sometimes primary producers

what are examples of decomposers and what is their source of energy?

bacteria & fungi, they obtain their energy from dead organisms by secreting enzymes that break down the organic matter

what are examples of detritivores and what is their source of energy?

Snails, slugs & vultures, derive their energy from detritus or decomposing organic material — dead organisms or feces or parts of an organism, ex: shed skin from a snake, a crab carapace

what is the function of detritivores and decomposers?

they provide a crucial service for the ecosystem: break down dead organisms, release the nutrients back into the cycle, control the spread of disease

food webs

complex network of interrelated food chains

what are limitations of food chains?

they are too simple; there are many organisms involved and one may eat several other species, species can feed at more than one trophic level and only illustrates a direct feeding relationship between one organism and another in a single hierarchy

pyramid of numbers

show the number of organisms at each trophic level in a food chain at one time - the standing crop

advantages of pyramids of numbers

simple, easy method of giving an overview and is good at comparing changes in population numbers with the time or season

disadvantages of pyramids of numbers

all organisms are included regardless of their size, therefore a pyramid based on an oak tree would be inverted, it does not allow for juvenlies or immature forms and the numbers can be too great to represent accurately

biomass

the quanitity of (dry) organic material in an organism, a population, a particular trophic level or an ecosystem

advantages of pyramids of biomass

overcomes some of the problems of pyramids of numbers

disadvantages of pyramids of biomass

only uses samples from populations, so it is impossible to measure biomass exactly, organisms must be killed to measure dry mass, the time of the year that the biomass is measured affects the result and pyramids of total biomass accumulated per year by organisms at a trophic level would usually be pyramidal in shape but two organisms with the same mass do not have the same energy content

disadvantages of pyramids of biomass and pyramids of numbers

snapshots at one time and place, depending on when the pyramid was investigated, for the same food web in the same ecosystem, the pyramid can vary with season and year

what does pyramids of productivity show?

the energy or biomass being generated and available as food to the next trophic level during a fixed period of time or the flow of energy over time

advantages of pyramids of productivity

most accurate sytem, shows the actual energy transferred and allows for rate of production, allows comparison of ecosystems based on relative energy flows, pyramids not inverted and energy from solar radiation can be added

disadvantages of pyramids of productivity

it is very difficult and complex to collect energy data as the rate of biomass production over time is required and the problem of assigning a species to a particular trophic level when they may be omnivores