Biology 2.6 - Ecology

“The study of how organisms interact with each other and their physical environment”

Definitions• Biosphere: The area (on Earth) where life is found• Species: Organisms with similar characteristics that are

able to interbreed to produce fertile offspring. eg cockles• Population: A group of organisms of the same species

that live in the same area at the same time. eg mud crabs at Warrington

• Community: All the populations of different species living and interacting in an area. eg bush community at Ross Creek

• Ecosystem: A community and the environment that it is found in. eg a mudflat ecosystem

• Biotic: The living factors of an environment. eg food supply

• Abiotic: The non-living factors of an environment. eg rainfall

• Habitat: The place where an organism lives. eg rock pools

Biosphere

The area (on Earth) where life is found

- ocean floor to upper atmosphere

Species

• Organisms with similar characteristics that are able to interbreed to produce fertile offspring. eg cockles

Austrovenus stutchburyi

Male Donkey

Female Horse

Mule (sterile)

Hinny (sterile)

Male horse

Female donkey

Mule vs Hinny

Mule more common “equine hybrid is easier to obtain when the lower chromosome count, the donkey, is in the male” - Wikipedia

Hinny smaller (due to smaller donkey uterus?), mane & head different… no difference also argued.

Population

• A group of organisms of the same species that live in the same area at the same time. eg barnacles at St Clair

Community

• All the populations of different species living and interacting in an area. eg bush community at Ross Creek

Ecosystem• A community and the environment that it is

found in. eg a mudflat ecosystem

Environmental Factors

Biotic Factors - The living factors of an environment. eg food supply

Organisms affect each other as:– Parasites– Pathogens– Symbionts– Predators– Herbivores– Competitors– Food supply…………..

Environmental Factors

Abiotic Factors - The non-living factors of an environment. eg temperature

Also:– Rainfall– Humidity– pH– Salinity– Light intensity………..

Environmental Factors on a Blue Cod

Wave action

Water temperature

Predators

Food supply

parasites

Dissolved oxygen

Human influence

salinitypH

Competition

Environmental Factors on a rabbit

Environmental Factors in a Rock Pool

• Biotic • Abiotic

Abiotic (Physical) Factors of soil in the School Garden:

• Temperature• Moisture• Salinity• pH• Soil profile• Infiltration• Aeration• Soil fertility• Soil particle size, organic matter content,

microbes, density, minerals

Physical Gradients• Most abiotic factors change with distance across

an environment (this creates different habitats and microclimates)

Habitat

• The place where an organism lives. eg rock pools

Habitat is defined by the abiotic and biotic factors found there

Wood Ear Fungus Habitat

Forest Floor

Biotic:- Feed on dead wood

Abiotic:- Cool temps- Moist soil- High humidity

Liebig’s Law of the Minimum*

“In most habitats there is one factor that determines how a species is distributed. This is the Limiting Factor and determines the distribution and numbers of a species”

Eg, in the outback the number of plants and how close they are is related to availability of water

Activity

• Nocturnal – active at night. eg morepork

• Diurnal – active during day. eg sheep

• Crepuscular – active at dawn/dusk. eg rabbit

Feeding

• Producer (autotroph): organism that makes own food, usually photosynthetic (usually plants, algae, some bacteria).

• Consumer (heterotroph): feeds on other organisms or dead matter.

• Carnivore: consumes animals. Wolf• Herbivore: consumes producers. Sheep• Omnivore: consumes producers & animals. Possum• Scavenger: consumes (large) dead organic matter

Slater, Worm, Crab• Decomposer or Detritivore or Saprophyte: breaks

down dead organic matter (more completely than scavengers). Fungi, Bacteria

AdaptationsInherited features that help an organism to survive in its

habitat!Different to adapting – this means getting used to

environment (eg your hairs stand on end when you are cold)

• Structural: physical structures. eg Waxy cuticle on leaves reduces water loss

• Physiological (functional): processes an organism carries out. eg Intestinal cells secrete enzymes to digest food.

• Behavioural: the way an organism acts (individually or corporately). eg Spiders spin web to catch food.

Adaptations of a Rabbit

S: widely spaced eyes S: powerful hind legs P: High reproductive rate P: Short gestation P: Many young in a litter B: Freezes when startled B: Stamps feet when startled

Adaptations of a Kea

Ecological Niche

• The ‘functional position’ of an organism in its environment

• Ecological Niche Includes:– Habitat– Feeding type– Activity times– Adaptations

?

Sealion Ecological Niche

• Feeding Type: Carnivore

• Activity: Diurnal

• Habitat: Coastal marine

• Adaptations: Fast swimmer, tolerates cold water…..

Slater (Porcellio scaber)Ecological Niche

(from research and experiments)

• Habitat– Biotic– Abiotic

• Feeding type

• Activity

• Adaptations– Physiological– Structural– Behavioural

Slater AdaptationsStructural•Hard Exoskeleton•Jointed, flexible exoskeleton•Many legs•Dark slater•Oval, thin shape•Gills•Antennae•Hooks on legs•Excrete directly thru exoskeleton•Uropods (two feet at back) take up water

Behavioural•Clumping•Avoid light•Curls when touched•Freezes when touch

Physiological•Excrete ammonia•Aerobic respiration•Cold blooded (ectothermic)•Haemolymph (blood) can carry oxygen•Dozens of young

Soil Moisture Table

Task: Describe a Plant’s Niche• Choose a plant from the school grounds.

– Name it, describe it’s ecological niche• Habitat

– Include the abiotic and biotic factors found there and measure them or describe them

• Feeding• Adaptations

– At least 1 structural, physiological, behavioural…

Hebe

Rhododendron

Task: Ecological Niche Poster• Pick an organism

– Name it, describe it’s ecological niche by giving its:

• Habitat– Include the abiotic and biotic factors found there and

measure them or describe them

• Feeding type / method• Activity times• Adaptations

– At least 1 structural, physiological, behavioural…

• Include 1 captioned pictureType your name. Print to colour, print enlarge to A3 by: click printer properties, paper, tick both print on a3 AND fit to print size. Best posters go to the pool room

Tolerance

For each abiotic factor (eg pH) each organism has the following:

• Optimum Range: where it functions best

• Tolerance Range: where it survives

• Zone of Stress: processes (eg respiration affected)

• Zone of Death: must move on or die!

Tolerance

Gause’s Principle“Organisms occupying the same niche

cannot co-exist because they compete for the same resources”

Eg flax caterpillars

Georgii Frantsevich Gause 1910–1986

Gause’s Principle eg Flax Caterpillars

Flax looper- Nocturnal feeder- Scrapes off flax, near

midrib (leaves translucent ‘windows’

Flax notch- Nocturnal feeder- Bite off edge of flax

(leaves notches)

Gause’s Principle“Organisms occupying the same niche

cannot co-exist because they compete for the same resources”

Aka – Competitive Exclusion Principle

Eg flax caterpillars – at first seem to be in direct competition, but actually occupy slightly different habitats.

Testing Gause’s Principle

• Aim: to determine if flax looper and notch caterpillars do occupy different microhabitats

• Hypothesis: I predict that the caterpillars do/not occupy different microhabitats

• Equipment: flax leaves with evidence of both caterpillars, ruler

• Method: – 1. Measure distance from mid rib of leave to middle of

each feeding location. – 2. Record as either looper or notch. – 3. Collate class data, analyse

ResultsFeeding location (distance from midrib) of flax caterpillars

Notch distance (mm) Window distance (mm)

Average: Average:

ConclusionsThe results show…because…

Niche Size…

• The full range of environmental conditions an organism can live in is the fundamental niche

• But, because it faces competition from other organisms it has to occupy a narrower set of conditions (to which it is best adapted). This is the realised niche

(kite graph OHT)

Population Features

Population: a group of organisms of the same species living in the

same area at the same time

Features of Populations

• Density• Distribution• Population Size• Migration• Sex ratios• Population Fertility• Age Structure• Population Growth Rate• Natality • Mortality

Population Size

• Number of organisms in population (abundance)

• How many penguins in the picture…?

1.Direct Count

2.Sampling

3.Mark & Recapture

Population Density

• Number of organisms per unit area

Low: territorial? solitary?

High: colonial? social?

Population Distribution

• Clumped – around resource, protection

• Uniform – evenly spaced

• Random – no pattern (plants, rare in animals)

Migration• Immigration – individuals entering population

• Emigration – individuals leaving population

• Both can affect: density + distribution, sex ratio, pop fertility, age structure

(Immigration – IN, Emigration – EXit)

Rural Urban Migration

Population Composition

• Sex Ratio: proportion of organisms of each sex

• Age Structure: proportion of organisms of different age groups (juvenile or prereproductives, reproductives, post reproductives)

Population Dynamics

• Population Growth Rate: number added to population per unit time (may be negative!)

• Natality (birth rate): number born per unit time

• Mortality (death rate): number dying per unit unit

• Equilibrium occurs when:

births + immigrants = deaths + emigrants

Age Structure, Sex Ratio• China's Population by Age & Sex, 1950 - 2050

(population in 1000)

(Right click to pause)

Features of Populations• Population Size: Number of organisms in population

(abundance)• Density: Number of organisms per unit area• Distribution: The location in the environment where the

organisms are found (clumped, uniform, random)• Migration: Individuals entering (immigration) or leaving

(emigration) the population• Sex ratios: ratio of male:female• * Population Fertility• Age Structure: proportion of organisms of different age

groups (juvenile or prereproductives, reproductives, post reproductives)

• Population Growth Rate: number added to population per unit time.

• Natality (birth rate): number born per unit time• Mortality (death rate): number dying per unit time

Estimating Population Size

Estimating Population Size1. Direct Count: Small populations, stationary organisms physically

count individuals

2. Sampling: Plants, slow animals Use transect lines + quadrats

Pop. density = av. Number per quadrat area of quadrat

Pop. Size = density x area

!! More sampling = more reliable result but more time,$...

3. Mark & Recapture (Lincoln index): Mobile animals catch & mark, proportion of marked animals recaught estimates pop.

Pop. Size = No. in sample 1 x No. in sample 2 No. animals recaptured

Lincoln Index• Used to find population size of large populations of

animals that move around too much to be sampled easily

• A sample of animals are caught, marked, released, given time to mingle with other animals then recaptured

• The percentage of marked animals recaptured helps you calculate the total population

For the statisitcians…n1 = number of animals first marked and released.n2 = number of animals captured in the second samplem2 = number of marked animals in the second sampleN = Total Population• The assumption is that the proportion of marked to non

marked animals in the second sample is the same as the proportion of marked animals to non-marked within the whole population.So…

m2/n2 = n1/N• Rearrange this to find N

N =  n1 x n2 / m2

Lincoln IndexNumber of animals in sample 1

xNumber of animals in sample 2

Number of marked animals in sample 2

Total Population =

S1=21

Issues

• Capture + Mark might injure, kill, change behaviour affect chance of recapture

• Mark may come off, affect predation rates• Assumes:

– all organisms have equal chance of capture (life stages, seasons, times of day, gender…)

– experimenter effort is the same– no migration, natality, mortality– individuals have had enough time to mingle since first capture– population is large

• Technique has been shown to be inaccurate when number recaptured is <8

Population RegulationFew species show continued exponential growth –

population growth and size is regulated by environmental factors in two ways:

• Density Independent Factors – affect all members of the population regardless of density (though some may be better adapted). Eg rainfall, temperature, humidity, floods, fire

• Density Dependent Factors – have a greater affect on the population when density is higher. Eg food supply, disease, parasites, competition, (predation)

Population Growth Curves

World Population

World population from 1800 to 2100, based on UN 2004 projections (red, orange, green) and US Census Bureau historical estimates (black).

Population Clock

Increase rate 1950–2000

Past & Predicted Continental Popns

Population evolution in different continents. The vertical axis is logarithmic and is millions of people.

Dramatic Human Negative Population Growth Examples

• The Plague of Justinian caused Europe's population to drop by around 50% between 541 and the 700s.

• The Black Death pandemic in the 14th century may have reduced

the world's population from an estimated 450 million to between 350 and 375 million in 1400. It took roughly 200 years for Europe's population to regain its 1340 level .

• The Toba supereruption (Young Toba Tuff or simply YTT[1]) occurred between 69,000 and 77,000 years ago at Lake Toba (Sumatra, Indonesia), and it is recognized as one of Earth's largest known eruptions. The related catastrophe theory holds that this supervolcanic event plunged the planet into a 6 to 10 year volcanic winter, which resulted in the world's human population being reduced to 10,000 or even a mere 1,000 breeding pairs, creating a bottleneck in human evolution. Some researchers argue that the Toba eruption produced not only a catastrophic volcanic winter but also an additional 1,000 year cooling episode.

Survivorship“the likelihood of death at any given age”

• Survivorship Curves show the number or proportion of individuals surviving at each age for a given species or group.

Type I High survival in young, rapid decline in survivorship in later life. Eg Humans

Type II Intermediate between Type I and III, where roughly constant mortality rate is experienced regardless of age. Eg Most birds

Type III Highest mortality in young, with lower mortality for older individuals. Eg Barnacles, frogs

r and K

Communities

Food Chains“diagram showing flow of energy through organisms”

• Start with a producer (usually a plant) which produces own food (photosynthesis) converting energy from sun into chemical potential energy (glucose). Aka autotrophs

• Arrows show path/direction of the energy• Consumers obtain energy from producers and other

consumers. Aka heterotrophs• Each organism occupies a specific feeding level or trophic

level (producers =1, herbivore =2…)• The first consumer in the chain is the “first order consumer”

or “primary” or “1º consumer” (then secondary, tertiary, quarternary)

• Food chains often have 4 links but seldom more than six (because, at best only 10% of the energy at each trophic level is passed on (energy lost as heat from respiration and wastes or “detritus”)

• Heat is always lost to the system but wastes can be utilised by decomposers or detritivores

Food Webs

“diagram showing all the linked food chains in a community”

(community = ALL the living organisms in an environment)

Community Patterns

Succession• Succession: Change in species composition

over time. Succession usually follows a predictable pattern.

• Primary Succession: succession starting with bare rock (eg: glacier retreat, new volcanic island). 100s 1000s of years.– Colonisers pioneer community intermediate

community climax community (stable species composition)

• “lichens mosses blown into site, colonise, erode rock, die, decompose creating simple soil, grasses and small shrubs able to grow – change occurs because each succession stage modifies environmental conditions, thus allowing new species to survive”

• Secondary Succession: succession starting after a previous community has been removed or “disturbed” (eg after fire, eruption, human influence). Faster than primary succession.

• Primary succession on Rangitoto Island

• Secondary Succession – Abandoned pasture, Poland

• Secondary Succession after wildfire in boreal pine forest, Estonia: two photos of the same place, picture on the left taken one year and picture on the right two years after the fire.

Succession…

Succession Animation

CSI and Succession!?Usually succession ends in a climax community. A special case is where degradative succesion occurs where eventually all species die off as the resource becomes exhausted. The resource is a corpse. Forensic entomology uses the principles of ecological succession to determine when a dead body began to compose. As a body decays moisture content and pH change in such a way that the types of insect species living on the corpse go through a predictable sequence of changes or succession.

The time since death is estimated by the species in the current community that are using the body as a resource. Over a period of 1-3 years there is a succession of 6 fly species.

How does Biodiversity change during a Forest Succession?

• Biodiversity = number of different species living in an area– Low in early succession stages– High in climax community– Unstable in early stages (few species, eg if the only

producer is wiped out everything dies)– Stable in a climax forest community (because large

number of different species and many interactions, eg if one food source is wiped out, a consumer may just change food source.

Case Study• A tree in a climax community falls over –

what will happen in terms of competition & biodiversity?

Stratification

“The vertical change in species composition”

Eg: Different organisms are found in different layers (strata) of a forest from the forest floor to the canopy

NZ Bush Strata• Emergent

– Rimu, totara

• Canopy– kamahi

• Sub-Canopy– Pepperwood, stinkwood

• Shrubs– rangiora

• Ground– Mosses, ferns

+ Epiphytes (plant growing on another plant eg bush lily)

Stratification in the Ocean?

Why does Stratification Occur?

• Each layer modifies the environmental conditions below it causing distinct layers of species adapted to that layer.

! This is what makes Stratification different from Zonation – zonation bands don’t alter conditions in other bands.

Why does Stratification Occur?

Abiotic factor Canopy Floor

Light intensity

Light quality

Wind speed

Humidity

Temperature

Zonation“A change in species composition across a

community in response to an environmental gradient.”

Gradient may be caused by abiotic or biotic factors

Eg: Zonation up a mountain: Distinct zones caused by varying exposure to wind, poorer soils, lower temps the higher you go

Rocky Shore Zonation

• Distinct zones caused by varying exposure to sea as tide rises & falls– At HWM abiotic factors important: most

exposure to air, highest air temps, greatest loss of water

– At LWM biotic factors most important: competition, predation, food supply, space

Rocky Shore Zonation

Additional Environmental Factors causing zones:• Exposure to temperature extremes• Fluctuations in salinity• Lack of food while the tide is out• Sufficient moisture to keep gas exchange

membranes moist• Amount of light• Wave action• Exposure to predators• Amount of space• Competition

Remember…

• Competition between organisms with similar environmental needs is a major factor in determining zonation

• This is reflected in the fact that realised niche is smaller than fundamental niche

Biodiversity

• The number of different species living in a particular area

Notes pages

Activity

• _________ – active at night. eg ________

• ________– active during day. eg _______

• ____________ – active at dawn/dusk. eg ________

Feeding• ________ (________): organism that makes own

food, usually ____________ (usually plants, algae, some bacteria).

• ________ (____________): feeds on other organisms or dead matter.

• ________: consumes animals. Wolf• ____________: consumes plants. Sheep• ________: consumes plants & animals. Possum• ________ (____________): consumes dead organic

matter (________ consume large organic matter). Slater, Worm, ________

• ___________: breaks down dead organic matter (more completely than detritivores). ______, Bacteria

AdaptationsInherited features that help an organism to

____________in its habitat!Different to ____________ – this means getting

used to environment (eg your hairs stand on end when you are cold)

• ____________: physical structures. eg Waxy ________ on leaves reduces ________ loss

• ____________ (functional): processes an organism carries out. eg Intestinal cells secrete ____________ to digest ________.

• ____________: the way an organism acts (individually or ____________). eg Spiders spin web to catch food.

Adaptations of a Rabbit_: widely spaced eyes

_: powerful hind legs

_: High reproductive rate

_: Short gestation

_: Many young in a litter

_: Freezes when startled

_: Stamps feet when startled

Succession• ______: Change in species composition over

____. Succession usually follows a predictable _____.

• _____ Succession: succession starting with bare rock (eg: ___ retreat, new volcanic island). ____s 1000s of years.– _______ _________ community

intermediate community _______ community (________ species composition)

• “lichens, ______ blown into site, ______, erode rock,

_____, decompose creating simple ____, grasses and

small shrubs able to _____ – change occurs because each

succession stage ______ environmental conditions, thus

allowing new ______ to survive”

• ________ Succession: succession starting after a previous community has been _________ or “disturbed” (eg after fire, eruption, human influence). _______ than primary succession.

_____________________________ ______________________________

Survivorship“the likelihood of _____ at any given age”

• _________ _______ show the number or proportion of individuals surviving at each age for a given species or _______.

______ High survival in ________, ______ decline in survivorship in later life. Eg ______

Type II ________ between Type I and III, where roughly __________ ________ rate is experienced __________ of age. Eg Most ________

Type III _______ mortality in ________, with lower ____________ for older individuals. Eg Barnacles, ________

Survivorship“the likelihood of _____ at any given age”

• _________ _______ show the number or proportion of individuals surviving at each age for a given species or _______.

______ High survival in ________, ______ decline in survivorship in later life. Eg ______

Type II ________ between Type I and III, where roughly __________ ________ rate is experienced __________ of age. Eg Most ________

Type III _______ mortality in ________, with lower ____________ for older individuals. Eg Barnacles, ________

Survivorship“the likelihood of _____ at any given age”

• _________ _______ show the number or proportion of individuals surviving at each age for a given species or _______.

______ High survival in ________, ______ decline in survivorship in later life. Eg ______

Type II ________ between Type I and III, where roughly __________ ________ rate is experienced __________ of age. Eg Most ________

Type III _______ mortality in ________, with lower ____________ for older individuals. Eg Barnacles, ________

Survivorship“the likelihood of _____ at any given age”

• _________ _______ show the number or proportion of individuals surviving at each age for a given species or _______.

______ High survival in ________, ______ decline in survivorship in later life. Eg ______

Type II ________ between Type I and III, where roughly __________ ________ rate is experienced __________ of age. Eg Most ________

Type III _______ mortality in ________, with lower ____________ for older individuals. Eg Barnacles, ________

Stratification

“The ________ change in species composition”

Eg: Different organisms are found in different layers (________) of a forest from the forest floor to the _____________

Why does Stratification Occur?

• Each layer __________ the environmental conditions below it causing distinct layers of species ________ to that layer.

! This is what makes Stratification different from Zonation – _________ bands don’t alter conditions in other bands.

Zonation“A change in species composition across a

community in response to an environmental gradient.”

Gradient may be caused by abiotic or biotic factors

Eg: Zonation up a mountain: Distinct zones caused by varying exposure to wind, poorer soils, lower temps the higher you go

Rocky Shore Zonation

• Distinct zones caused by varying exposure to sea as tide rises & falls– At HWM abiotic factors important: most

exposure to air, highest air temps, greatest loss of water

– At LWM biotic factors most important: competition, predation, food supply, space

Rocky Shore Zonation

Additional Environmental Factors causing zones:• Exposure to temperature extremes• Fluctuations in salinity• Lack of food while the tide is out• Sufficient moisture to keep gas exchange membranes moist• Amount of light• Wave action• Exposure to predators• Amount of space• Competition

Remember…

• Competition between organisms with similar environmental needs is a major factor in determining zonation

• This is reflected in the fact that realised niche is smaller than fundamental niche