Topic 4.1 – Species, Communities, Ecosystems
Understandings Species are groups of organisms that can potentially interbreed to produce fertile offspring.
Members of a species may be reproductively isolated in separate populations.
Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods).
Consumers are heterotrophs that feed on living organisms by ingestion. Detritivores are heterotrophs that obtain organic nutrients from detritus
by internal digestion. Saprotrophs are heterotrophs that obtain organic nutrients from dead
organisms by external digestion. A community is formed by populations of different species living together
and interacting with each other. A community forms an ecosystem by its interactions with the abiotic
environment. Autotrophs obtain inorganic nutrients from the abiotic environment. The supply of inorganic nutrients is maintained by nutrient cycling. Ecosystems have the potential to be sustainable over long periods of
time
Topic 4.1 – Species, Communities, Ecosystems
Skills and Applications Skill: Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode of nutrition.
Skill: Setting up sealed mesocosms to try to establish sustainability. (Practical 5)
Skill: Testing for association between two species using the chi-squared test with data obtained by quadrat sampling.
Skill: Recognizing and interpreting statistical significance.
What is a SPECIES? Group of organisms that can potentially interbreed and
produce fertile offspring
Similar physiological and morphological characteristics
Can produce fertile offspring (hybrids are not fertile!)
Genetically distinct from other offspring
Have a common phylogeny (family tree)
The interbreeding and interacting members of a species is called a POPULATION
Members of species may be reproductively isolated in separate populations
What are COMMUNITIES? An ecological community consists of all the interacting
populations in an area
The populations in a community interact in the following ways: predation, parasitism, competition
What are ECOSYSTEMS?
of all of the communities within a defined area, along with the ABIOTIC (nonliving) environment
study of ecosystems focuses on the flow of energy and nutrients
pathways of energy and nutrients to understand the factors shape interactions within communities, and between communities and the nonliving environment
Topic 4.2 – Energy FlowUnderstandings
Most ecosystems rely on a supply of energy from sunlight.
Light energy is converted to chemical energy in carbon compounds by photosynthesis.
Chemical energy in carbon compounds flows through food chains by means of feeding.
Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
Living organisms cannot convert heat to other forms of energy.
Heat is lost from ecosystems.
Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.
Topic 4.2 – Energy FlowSkills and Applications
Skill: Quantitative representations of energy flow using pyramids of energy.
How do Energy and Nutrients move through ecosystems? Nutrients are atoms and molecules that organisms obtain from
their living or nonliving environment and that are required for survival
constantly cycle and recycle within and among ecosystems
change in form and distribution
Energy moves in a one-way flow through communities within ecosystems
continuously replenished
used and transformed in the chemical reactions that power life
ultimately converted to heat that radiates back into space
Energy Flow Through Ecosystems
Energy enters ecosystems mainly through photosynthesis
energy stored in the chemical bonds of sugar molecules
produce food using nonliving nutrients and sunlight
Autotrophs: have the ability to make their own organic molecules
PHOTOSYNTHESIS – uses light energy and inorganic molecules to produce organic molecules
CHEMOSYNTHESIS – uses inorganic molecules such as hydrogen sulfide to produce organic molecules (instead of sunlight)
Sugar issynthesizedand used inplant tissues
planttissues,growth
Energy iscapturedfromsunlight
Carbon dioxideis absorbedfrom the air
Oxygen isreleased
Water is absorbedfrom soil, used inphotosynthesis, andstored in cells
Inorganic mineral nutrients(nitrate, phosphate) areabsorbed from soil andused in plant tissues
photosynthesis
O2
CO2
H2O
sugar
plant tissues
othernutrients
energy from sunlight
photosynthesis
Photosynthesis
Fig. 28-1
Energy Flow Through Ecosystems
Energy passes from one trophic level to another.
producers (autotrophs)
first trophic level
primary consumers (herbivores)
second trophic level
feed on producers
Secondary consumers (carnivores & omnivores)
Tertiary consumers
third and fourth trophic levels
meat-eating predators
Decomposers
Everything dies and nutrients must be brought back into cycle
Detritivores, Saprotrophs
Energy Flow Through Ecosystems
TERTIARY CONSUMER(4th trophic level)
PRODUCER(1st trophic level)
A simple terrestrial food chain(a)
SECONDARY CONSUMER(3rd trophic level)
PRIMARY CONSUMER(2nd trophic level)
Energy Flow Through Ecosystems
SECONDARY CONSUMER(3rd trophic level)
A simple marine food chain(b)
PhytoplanktonPRODUCER
(1st trophic level)
ZooplanktonPRIMARY CONSUMER
(2nd trophic level)
TERTIARY CONSUMER(4th trophic level)
Energy fromsunlight
detritus feedersand decomposers
primary consumers
producers
HEAT
higher-levelconsumers
HEAT
HEAT
NUTRIENTS
heat energy
solar energy
energy storedin chemicalbondsnutrients
HEAT
solar energy
heat
heat
heat
heat
nutrients
heat energy
energy stored inchemical bonds
detritus feedersand decomposers
primaryconsumers
higher-levelconsumers
producers
energy fromsunlight
nutrients
OSP
N
MgH
CaH2O
Can you identify the different trophic levels?
Energy Flow Through Ecosystems
An ecosystem’s contribution to Earth’s productivity depends upon both the ecosystem’s net primary productivity per unit area and its prevalence.
desert (90)
openocean(125)
continentalshelf (360)
tundra(140)
coniferousforest (800)
temperatedeciduousforest (1,200)
grassland (600)
tropicalrain forest(2,200)estuary
(1,500)
Energy Pyramid for a Grassland
Fig. 28-6
biological magnification
Because of the inefficiency of energy transfer, certain persistent toxic chemicals become increasingly concentrated in the bodies of animals that occupy increasingly higher trophic levels by a process called
Mercury taken up by producers can be highly concentrated in carnivores such as swordfish, and are a health hazard to humans as a result