4a: The Organism in the Environment

population

a group of organisms of the same species living in the same place at the same time

community

all of the populations living in the same area at the same time

interdependence

if one species is removed from a community it can affect the whole community

habitat

place where an organism lives

ecosystem

all the biotic factors and all the abiotic factors that interact within an area at one time

biotic factors

living components

abiotic factors

non-living components

do ecosystems vary in size and scale

yes

what does ecology study

* distribution of species
* abundance of species
* interactions between species
* interactions between species and their abiotic environment

ecologists

biologists that study interactions by investigating ecosystems

quadrat

square frames made of wood or wire used to investigate population size

how do we use quadrats

they are placed on the ground and the organisms within them are recorded

what do quadrats help estimate

commonly the abundance of plant species

what do we record to measure abundance in a quadrat

* number of individual specoes
* species richness
* percentage cover

species richness

total number of different species is recorded

percentage cover

approximate percentage of the quadrat area in which an individual species is found is recorded

when do we use percentage cover in investigating population size

when it is difficult to count individuals

investigating population size in 2 different areas using quadrats - apparatus

* 2 tape measures
* quadrat
* random number generator
* species key

investigating population size in 2 different areas using quadrats - method

* use tape measures to lay out a survey area
* use random number generator to create a set of coordinates to place first quadrat
* count number of chosen species within quadrat
* repeat for second quadrat
* estimate population using equation

investigating population size in 2 different areas using quadrats - equation for estimated population size

(total area / area sampled) x total number of species population counted

investigating population size in 2 different areas using quadrats - results

compare abundance of study species in each survey area

biotic factors influencing species abundance

* competition
* predator-prey relationships
* interactions with other organisms within food chain

abiotic factors influencing species abundance

* light intensity
* mineral availability
* water availability
* pH
* temperature
* salinity

investigating population size in 2 different areas using quadrats - limitations

* missing individual organisms when counting in a quadrat
* difficult to identify species

investigating population size in 2 different areas using quadrats - CORMS

C - study area

O - same species of quadrats

R - repeat for reliability

M1 - number of designated study species

S - size of quadrat, random way of quadrats, day of investigation

biodiversity

range and variety of different species of organisms on earth or within an ecosystem

what does biodiversity consider

* species richness
* variation within species
* distribution and population size of species

high biodiversity

* lots of different species
* lot of variation
* even distribution

how is biodiversity reduced

by human activities

what do different species depend on each other for

* food
* shelter
* maintenance of physical environment

advantages of a high biodiversity

* stability of ecosystems
* reduced dependence
* resilient to environmental impacts

what is a food web used for

to demonstrate the importance of biodiversity in an ecosystem

measuring biodiversity - apparatus

* 2 tape measures
* quadrat
* random number generator
* species key

measuring biodiversity - method

* use tape measures to lay out survey area
* use random number generator to create a set of coordinates for first quadrat
* count number of different species within quadrat
* repeat for 10 quadrats
* repeat for second survey area

measuring biodiversity - results

* compare number of different species
* \

measuring biodiversity - high biodiversity

larger number of different species

how is the measurement of biodiversity simplistic?

doesn’t tell us about distribution or population size

measuring biodiversity - limitations

* easy to miss individual organisms
* identifying and distinguishing between species

measuring biodiversity - CORMS

C - study area

O - same species of quadrats

R - repeat for reliability

M1 - number of designated study species

S - size of quadrat, random way of quadrats, day of investigation

abiotic factors that affect a community

* light intensity
* temperature
* moisture levels
* soil pH and mineral content
* wind intensity and direction
* carbon dioxide levels
* oxygen levels

light intensity

needed for photosynthesis

temperature

affects rate of photosynthesis

moisture levels

water for survival

wind intensity and direction

affects transpiration

carbon dioxide levels

required for photosynthesis

oxygen levels

aquatic animals need high oxygen concentrations

biotic factors that affect a community

* availability of food
* new predators
* new pathogens
* competitions

availability of food

more food = higher chance of surviving and reproducing

new predators

unbalances the ecosystem

new pathogens

population may decline as a result of lack of immunity and resistance

competition

if two species compete for resources and one is better adapted, then that species will outcompete the other