4.1 Species, Communities and Ecosystems

Life on Earth levels

cells, tissues, organs, systems, organisms, population, community, (+habitat) ecosystem, biome, biosphere

Ecology

the study of relationships between living organisms and their environment

Population

a group of organisms with the same: species, enviro and time

Ecosystem

a community + its abiotic factors

Community

a group of populations living and interacting with each other in the same environment

Habitat

the environment / location where a living organism lives and exists

species

a group of organisms that can interbreed to produce fertile offspring

features of species

* common gene pool
* common phylogeny
* recognition / communication is achieved by displays: dances, song calls, color, scent

Phylogeny

family tree

Limitations of the species definition

* cross-species breeding may occur but offspring are still usually infertile
* this ensures that gene pool is maintained and not mixed
* e.g Mule = horse + donkey but cannot breed

Reproductive isolation by separate populations

* unlikely to interbreed due to sep. populations
* there is still a chance that they can interbreed when brought together
* hence still the same species

Reproductive isolation by geographical / physical isolation

* cannot interbreed due to physical / geo barrier
* there is no chance that they can interbreed when brought together
* hence two different species

What is an autotroph

* produces their own food from organic molecules
* light or chemical energy synthesizes their food

what are producers

* an autotroph - makes their own food
* can perform either photoautrophy or chemoautrophy

photoautrophy

* photosynthesis
* e.g green plants, algae

chemoautrophy

* chemosynthesis
* e.g chemosynthetic bacteria

what are heterotrophs

organisms that derive energy from other living organisms

Consumers

eat matter that was killed recently

Decomposers

organisms that break down dead or decaying organisms

Primary Consumers

herbivores

Secondary Consumers

carnivores and omnivores

Detrivores

* eat non living organic matter e.g earthworms


* internal digestion

Saprotrophs

* living in / on other living matter
* secret digestive enzymes in and eats their digestive products
* external digestion

Exceptions to feeding methods table

* Parasitic plant species
* don’t photosynthesise but grow on other plants and obtain their carbon compounds (therefore harmful)

Trophic levels

Heterotrophs:

* 2ndary predator
* primary predator
* herbivore

Authotrophs:

* plants

SOIL

Heterotrophs:

* Decay detrivores

Exceptions to the trophic levels

most consumers don’t fit into one trophic level because they consume food from many areas / different levels

Why are Saprotrophs important?

* important in the role of decay of dead organic matter
* breaks down carbon compounds
* releases elements (N and C) into environment so can be used again by others

Abiotic factors

* non living factors
* abiotic influence biotic e.g bigwave
* biotic influence abiotic e.g tree grow betw rocks

List examples of abiotic factors

* temperature
* PH
* light levels
* humidity
* sunlight hours
* rainfall
* soil salinity

Outline Nutrient cycling in autotrophs

* INORGANIC → ORGANIC
* obtain inorganic nutrients from abiotic enviornment and convert into organic compounds

Outline Nutrient cycling in heterotrophs

* ORGANIC → INORGANIC
* obtain nutrients by consuming other organisms
* uses this for respiration and growth and releasing inorganic compounds as a product

Why is nutrient cycling important?

* earth = a closed system, amount of matter remains the same
* energy flows through earth but nutrients must be recycled bc limited
* all elements must be recycled in order for life to exist

Nutrient cycling vs Energy Flow

* nutrients can be recycled indefinitely
* energy cannot be recycled - must be constantly be supplied by the sun

When are ecosystems sustainable?

* nutrients are available
* detoxification of wastes (used as food source)
* energy is available (cannot be recycled)

What happens when consumers die?

digestive enzymes break down their cells and return their nutrients to the soil