IBDP ESS-SL Topic 2.1 STRUCTURES

By Peter Stanley, International School of Tanganyika, 2008

Modified by Brad Kremer, International School of Tanganyika, 2011

2.1.1 Biotic vs. Abiotic“Distinguish between biotic and abiotic (physical) components of an ecosystem.”

(2)

Biotic (alive)• biotic components in an ecosystem include all living things AND their interactions

Abiotic (non living)• physical parts of an ecosystem

Where do these fit?

predationaltitude

soil pH wind speed

temperature

humidity

light intensitymutualism

trees

parasitism

precipitation

2.1.2 Trophic levelsDefine trophic level. (1)

• A trophic level is where an organism is positioned according to its feeding relationship to other organisms.

• Each successively higher trophic level contains less energy and biomass than the trophic level immediately below it.

Egyptian Cobra

Grass Acacia Tree Shrub

Field Mouse Weaver Bird

Secretary Bird Tawny Eagle

Serval Cat– Quaternary (4˚) consumer– Tertiary (3˚) consumer– Secondary (2˚) consumer– Primary (1˚) consumer– Producer

Quaternaryconsumers

Tertiaryconsumers

Carnivore

Carnivore

Secondaryconsumers

Carnivore

Primaryconsumers

Herbivore

Primaryproducers

Producer

A terrestrial food chain

grass tree

Eagle

mouse

cricket butterfly

weaver

termite

2.1.3 Trophic levels in chains and webs“Identify and explain trophic levels in food chains and food webs selected

from the local environment.” (3)

Click to try another web

2.1.4 Pyramids“Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data.” (3)

Pyramids show the quantitative (number) difference between trophic levels of a single ecosystem.

We will explore 3 kinds of Pyramids used in ecology:1.Pyramids of numbers

2.Pyramids of biomass

3.Pyramids of productivity

• These type of pyramids tend to follow the 2nd law of thermodynamics (there is a tendency for numbers and biomass and energy to decrease along a food chain).

storage

movement

2.1.4.a Pyramids of NumbersTrophic levels usually found with more numbers of organisms at the bottom and fewer at the top... a pyramid of numbers.

2˚ Consumer2˚ Consumer

1˚ Consumer1˚ Consumer

3˚ Consumer3˚ Consumer

ProducerProducer

When might it not be in the shape of a pyramid? (hint: just think #’s)

1 tree, 1000 termites, 20 geckos, 1 crow

2.1.4.b Pyramids of BiomassBio (life)... mass (~weight)•This is a measure of the stock (storage) of each trophic level at a specific moment (not over a long period of time).•The units used are:

•Mass => g / m2

or•Energy => J / m2

When might the data result in a shape other then a pyramid? (hint: “at a specific moment in time”)Need another hint? brrrrrrrrrrrrrrrr

Winter or seasonal changes that significantly reduce the biomass for producers.

2.1.4.c Pyramids of Productivity

also known as Energy Flow PyramidsNOT “Energy Pyramids” which show a stock of energy at

each trophic level at one moment.Productivity/flow of energy

•flow of energy through a trophic level over time•units => g / m2 /yr or J / m2 / yr

• Energy transformations are never 100% efficient. Feces, respiration and heat are all ways in which energy is used and not available for the next trophic level.

Feces100 J

Growth (new biomass)

33 J

Cellularrespiration

67 J

200 J200 J

Plant materialeaten by caterpillar

Math Check!

2.1.4.c Energy Efficiency in Pyramids of Productivity

2.1.4.c Pyramids of Productivity10% Rule

Only 10% of the energy is

taken in by the next tropic

level!

by Pearson Education

2.1.5 Effects of Pyramids“Discuss how the pyramid structure affects the functioning of an ecosystem.” (3)Biomagnification of DDT in the food chain... the affects can be seen clearly in a pyramid.

2˚ 2˚ ConsumerConsumer

1˚ Consumer1˚ Consumer

3˚ Consumer3˚ Consumer

ProducerProducer

D

D

T

2.1.6 Definitions“Define the terms species, population, habitat, niche, community and

ecosystem with reference to local examples.” (1)•Species: a group of organisms which can interbreed and produce fertile offspring. •Population—a group of organisms of the same species who live in the same area at the same time. •Habitat—the environment in which a species normally lives or the location of a living organism •Niche - a position/role taken by an organism in a community•Community—a group of populations living and interacting with each other in an area. •Ecosystem—a community and its abiotic environment. •Ecology—the study of relationships between living organisms and between organisms and their environment.

2.1.7 Population interactions“Describe and explain population interactions using examples of named species.” (3)

Competition• competing for what?Parasitism•parasite benefits, host is harmedMutualism•both species benefit (symbiotic)Predation•hunting of prey by predatorsHerbivory• consumers eating producers

Using any reliable source in class to complete this list below:

Predation