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