Topic 4.1 - Species,Communities and Ecosystems
ECOSYSTEM = community + abiotic environment ( soil, water, rock i.e )
SPECIES = group of organisms that can inbreed/ produce fertile offspring
Impossible for two different species to produce fertile offspring if not closely related
Closely related species (i.e donkey & horse) can produce sterile offspring ( mule )
HABITAT = environment species lives or location of living organism
POPULATION = group of organisms of same species living in same area/time
Organisms of same species separated geographically ( different area) and temporally (
different time ) unlikely to interbreed (reproductively isolated)
Two populations living in different areas unlikely to interbreed. Does not mean they are
not same species
Species never interbreeding may result in them gradually developing different
characteristics
BUT…
Species only considered same species until they can no longer interbreed/ produce
fertile offspring
COMMUNITY = group of different species living/interacting with each other in same area
All dependant on each other for long-term survival ( i.e symbiont relationship, lion
depending on prey for food )
AUTOTROPHIC AND HETEROTROPHIC NUTRITION
➔ Species have either autotrophic or heterophobic methods of nutrition ( few have both )
➔ Some unicellular organisms use both
AUTOTROPH = organism that synthesizes its organic molecules from inorganic substances (
self-feeding )
Capable of making their own food through photosynthesis
Converts sunlight (light energy) into organic molecule (glucose)
Also called producers
I.e cyanobacteria, algae, grass and trees
HETEROTROPH = organism that obtains organic molecules from other organisms ( feeding on
others )
MIXOTROPH = organism that uses both methods of nutrition ( self-feeding and feeding on
others)
NATURE OF SCIENCE: TRENDS IN PLANT AND ALGAL NUTRITION
●
●
●
●
Most plants/algae are autotrophic
Majority make own organic compounds (glucose) through photosynthesis in chloroplasts
Plants that do not have chloroplasts/do not perform photosynthesis ( Only 1%) = parsitic
Original species believed to be autotrophic and parasitic species evolved from them
CONSUMERS = heterotroph that feeds on living organisms by ingestion
●
●
●
Heterotrophs cannot make own organic matter ∴obtain organic molecules from other
organisms
Rely on organism (either alive or dead/decomposing) for food
Use range of different food sources/feeding mechanisms
HERBIVORES ( i.e zebra, deer ) feed on producers (plants)
↓
OMNIVORES ( e.g mouse, chimp ) feed on combination ( both producers & consumers )
↓
CARNIVORES ( e.g lions, snakes ) feed on other consumers
↓
SCAVENGERS = specialized carnivores, feed on mostly dead/decaying animals (e.g
hyenas,vultures, crows)
Consumers divided into trophic groups according to what they eat:
PRIMARY CONSUMERS feed on AUTOTROPHS
SECONDARY CONSUMERS feed on PRIMARY CONSUMERS
DETRITIVORES and SAPROTROPHS
DETRITIVORE = heterotrophic organism that ingests non-living (dead) organic matter by
internal digestion
●
●
●
Ingest organic matter ( i.e dead leaves, other plant parts, feces, or animal carcasses)
Digest it internally absorbing productions of digestion
I.e earthworms, woolice, dung beetles, bottom feeders in rivers & oceans
SAPROTROPH = heterotrophic organism that lives on/or in non-living ( dead) organic matter,
secreting digestive enzymes into it and absorbing products of digestion
●
●
●
●
Unlike heterotroph, they are not consumers/ do not ingest food
Important in role of decay of dead organic materials
Also called decomposers (they help break down waste materials & release elements
such as nitrogen into ecosystem to be used by other organisms)
i.e fungi & bacteria
SKILL: IDENTIFYING MODES OF NUTRIENT
Either ingests organic matter ( no cell walls) or by taking it into guts
CONSUMERS
Feeding on living/recently killed organism
DETRITIVORES
Feeding on dead organic matter
Cell wall present. No ingestion of organic matter. No gut
INORGANIC NUTRIENTS
●
●
●
inorganic molecules = carbon,hydrogen, oxygen,nitrogen,phosphorus & others,
heterotroph/autotroph obtain from abiotic environment
Autotroph obtain elements they need from abiotic environment i.e carbon & nitrogen
Heterotrophs obtain some elements from carbon compound in food/others from abiotic
environment i.e sodium,potassium & calcium
NUTRIENT CYCLES
●
●
●
●
●
Limited supply of nutrients on earth
Inorganic nutrients maintained by nutrient cycling
Organisms absorb needed elements as inorganic nutrients, use them and return them to
environment
Autotrophs convert nutrients from inorganic to organic molecules i.e CO2 →glucose
Heterotrophs ingest other organisms, gain energy & release nutrients back into soil to
ensure availability to other organisms
SUSTAINABIlTY OF ECOSYSTEM
●
●
Relatively little energy & nutrients flows enter/or leave ecosystems
Ecosystems = self-contained & self-sustaining
●
Requirements for sustainability of ecosystem:
○ Nutrient availability ( saprotroph crucial for continuous provision of nutrients)
○ Detoxification of waste products( e.g decomposing bacteria derive energy from
breakdown of toxic molecules into simpler, less toxic substances)
○ Energy availability ( light form = sun)
Nutrients can be recycled indefinitely, no lack of chemical elements
Energy cannot be recycled, depends on continuous supply of energy from Sun
●
●
MESOCOSMS
●
●
●
Biological systems with features of abiotic/biotic environment
Restricted in size & under controlled conditions
Used for scientific research/to collect data