Friday, October 19th: Period E

• 1. An update on EXCEL 2011• 2. Homework Review• 2. Completing Topic G.1, Community Ecology

EXCEL – Revised, Improved Worksheet…

• Please complete your temperature assignment by Tuesday. The worksheet (revised for EXCEL 2010) is accesible on the Class Blog

• Please contact me if you don’t have access to EXCEL, or if you need some help

• Use your IB Independent Assessment Guide – it has all of the answers to your questions!!

• Online help:• Getting started with EXCEL

Homework Review: Factors Affecting Plant and Animal Species

Distribution

i-Biology Link

i-biology hyperlink

Homework Review: Relationships Between Species

Relationships Between Species

RELATIONSHIP SPECIES 1 SPECIES 2

HERBIVORY Plant: +/- Primary Consumer +

PREDATION Predator: + Prey: -

PARASITISM Host: - Parasite: +

MUTUALISM Species 1: + Species 2: +

(COMMENSALISM) Species 1: 0 Species 2: 0

COMPETITION +/-/0 +/-/0

Let’s Check those relationships…

• It's David....(3.30)• National Geographic Anemones/clownfish• PBS marine interactions• Marine Mutualism

COMPLETING Topic G:1

•Competition!• The niche concept

•Competitive exclusion•Niche partitioning

‘Competition’ in Ecology?When does it happen?• Shared resource in short supply• Competion is a density dependent determinant of population

dynamics

Do competitors have to meet each other?

Competition can be between individuals of the same species

(intra-specific) or between different species (inter-specific)

Intra-specific competition: Competition for mates

• Male Bighorn Sheep• Bisons headbutting

Intra-specific competition: Darwin’s Finches

• Darwin's Finches

Interspecific CompetitionCompetition between different species which depend on the

same resource:• Food• Water

• Nesting Sites• Breeding Sites

Examples:Competition...in spades...

The Niche Concept

Topic G.1.5: Explain what is meant by the niche concept, including an

organism’s spatial habitat, its feeding activities and its interactions with

other species

The Niche Concept: Definition

‘Nicher’ (French): to Nest• A term describing the way of life of a population• To describe a population’s niche, you need to

describe its ‘specialised habitat’: – space and territory– Nutrition and feeding habits– Interactions with other organisms– Its reproductive habits– Its role in the community

The Niche concept: A Working Analogy

In 1927, Charles Sutherland Elton, the British Ecologist, stated: ‘When an ecologist states ‘There goes a badger’, he should include in his thoughts a definite idea of the animal’s role in the community, just as if he had said ‘There goes the vicar’

Defining a Niche : ‘The Boundary conditions’

Two species that use exactly the same resources cannot

occupy the same nicheOnly one species or

population can occupy the same niche for an

extended period

G.1.8: Distinguish between fundamental and realized

niches.

Fundamental Niche

A species’ fundamental niche is the full range of environmental and social conditions under which it

could potentially survive and reproduce‘potential niche’

• Some species have a broad fundamental niche• Some species have a narrow fundamental niche

Realised Niche

The realised niche is the specific set of conditions in which it survives in a given habitat or ecosystem, given the other species or limitations present.These are the conditions to which the population is best adapted.

‘Realised Niche’ is not a constant for a species

• In fact, populations of the same species may occupy different realised niches within different ecosystems

• It all depends on the other species and environmental factors involved in ‘sharing of the resources’

Let’s look at some examples….

G.F. Hutchinson’s Definition of the Hyperdimensional Niche…

Homework for Monday

• Research information for two species of your choice.

• One can be the Clown-fish• The other can come from the WWF website:• WWF species directory

G.1.7: Explain the principle of competitive exclusion

Aka ‘Gause’s Law’

‘No two species can occupy the same niche for a prolonged time’

The Competitive Exclusion Principle• If two species share a

niche, there must be inter-specific competition for resources

• The best adapted species will survive

• The loser will struggle to survive and reproduce, and will eventually become extinct OR migrate (if its niche is broad enough)

Examples are abundant• Invasive species• Red versus Grey

Squirrel in Western Europe

• Gause’s Paramecium

Competitive Exclusion: Squirrels

Competitive Exclusion: Squirrel Distribution

G.1.7: Outline the method and importance of G.F. Gause’s paramecium experiments

Gause's Struggle for existence can be accessed in full online (even in Russian!)!

G.1.7: Outline the method and importance of G.F. Gause’s paramecium experiments

Georgy Gause cultured 2 species of the protist Paramecium:• P. Aurelia• P. Caudatum• Grown together under ideal

conditions, both populations reach a higher maximum

• Grown together, one species rapidly becomes extinct…

Let’s think about it…..How does environmental change

affect a species with a broad niche?

Species with a broad niche

• ‘Generalists’• Widely distributed

geographically• Adaptable

Red-Tailed Hawk

Let’s think about it…..How does environmental change

affect a species with a narrow niche?

Species with a narrow Niche

• ‘Specialists’• Not adaptable• Under threat of

extinction if the niche changes

Does Competitive Exclusion work in the real world?....

The competitive Exclusion principle is actually rarely observed in natural ecosystems:• ‘spatial heterogenity’ (niche partitioning)• Niche sharing/ partitioning associated with

availability of multiple resources• ‘The paradox of the plankton’: Why do so

many plankton species exist in a small, limited, homogenous habitat?

Niche Partitioning

As there is a limited about of space and resources on Earth, organisms can use niche partitioning1. Spatial: Two different species use the same resource by occupying different areas within the range of the resource2. Temporal: Two species eliminate direct competition by using the same resource at different times 3. Morphological: Two different species evolve different morphologies in order to use a resource in different ways

Spatial Niche Partitioning

Closely related bird species

occupy different foraging locations

on a single tree species

Temporal Niche Partitioning

Different species of spiny mouse inhabiting the same ecosystem may be either nocturnal OR diurnal feeders

Morphological Niche Partitioning

Different beak sizes have allowed

adaptive radiation of finches in the

Galapagos Islands