OPTION G

OPTION G

G 1, G 2, G 3SL TOPICS

G1 Community ecology Abiotic factors that effect distribution of plant species

Discuss how each factor affects plants species• Temperature (determines plant communities, desert plants show specific

adaptations)Why does temperature affect plants distribution?

• Water (determines plants species desert plants?) Why does water determine plants species in an ecosystem?

• Light Why does light affect plants distribution?

• Soil pHHow does pH of soil and water affect plants? Acid rain?

• SalinityEffect of salt on plants? Link osmosis. Halophytes live in salt marshes.

• MineralsWhy are minerals important for plants? pH and mineral uptake relationship?

• Temperature: How does temperature affect animals distribution? Cold blooded and warm blooded animals? Thermoregulation adaptations?

• WaterAnimals adaptation to desert? For habitat or reproduction

• Breeding sitesMany animals need special breeding sites. Salmon

• Food supplyMany animals have special diet. Humming birds eat nectar. Panda bears?

• TerritorySome animals need special territory. Ex. Tigers

Discuss how each factor affects animals species

Ecological Sampling

• What is a sample?– “A portion, piece, or segment that is representative of

a whole”

• Why do we sample?– it is usually impossible to measure the whole

One big assumption…

• That the sample is representative of the whole• It is necessary to take enough samples so that

an accurate representation is obtained• It is important to avoid bias when sampling

Sampling Methods

• Transects and Quadrants– Plants and Non-motile animals

• Lincoln Index• Capture –Mark- Recapture

– Small animals

• Aerial observations– Large trees and animals

Sampling along Transects

• Samples taken at fixed intervals• Set up along an environmental gradient (e.g.

high to low on a mountain)

Line transect method

• A measured line laid across the area in the direction of the environmental gradient

• All species touching the line are be recorded along the whole length of the line or at specific points along the line

• Measures presence or absence of species

Belt transect method

• Transect line is laid out and a quadrant is placed at each survey interval

• Samples are identified and abundance is estimated– Animals are collected– For plants an percent coverage is estimated

• Data collection should be completed by an individual as estimates can vary person to person

Quadrats

• Used to measure coverage and abundance of plants or animals

• A grid of known size is laid out and all the organisms within each square are counted.

Lincoln Index

• Capture-Mark-Recapture– Animals are captured,counted, tagged and released.– After a period of time another capture occurs.– Previously tagged animals are counted and unmarked

organisms are marked. – Abundance is calculated using the following formula:

n1 x n2

n3

n1=total marked after catch 1

n2=total marked after catch 2

n3=total caught in catch 2 but marked in catch 1

Measurements

• Sampling methods measure – Density– Coverage– Frequency– Biomass– Diversity

Density (D)

• The number of individuals per unit area– D=ni/A

– Eg. 10 dandelions/m2

• Relative density i (Rdi) – The Density of species i, Di, Divided by the sum of all

the densities of the other species sampled

– Rdi=Di/S D

– Eg. 10/5+8+16

ni=number of individuals for species i

A=the area sampled (could be the volume V)

Coverage (C)

• The proportion of ground that is occupied or area covered by the plant/species– Ci=ai/A

• Relative coverage– The Coverage of species 1, Ci, divided by the sum

total of the coverage of the other species sampled

ai=the area covered by species i

A=the total area

Frequency (f)

• The number of times a given event occurs– Eg. the number of quadrants that contain maple trees

as a ration of all the quadrants

– fi=ji/k

• Relative frequency– The frequency of species i relative to the sum total of

the frequencies of the other species found

ji=number of quadrants with species i

k=total number of quadrants

Biomass (B)

• Can be calculated by measuring the mass of the individuals per unit area

– B= S W/A

– More appropriate measure than density or frequency when

• Number of individuals in hard to determine• Photosynthesis and carbon fixation, energy and nutrient

transfer are more dependent upon biomass than the total number of individuals

Biomass Measurement methods

• Fresh or wet weight – Used when organisms are alive

• Dry weight– Used when the water content varies greatly– Oven dry at 105oC to remove water

• Ash-Free Weight– Used when inorganic content varies greatly– Oxidize at 500oC until only inorganic ash remains

Diversity

• The measure of variety of an ecosystem • Consists of 2 components

– The number of different species or the richness of species in a specific area

– The relative abundance of the individuals of each species in a specific area

Simpson's Diversity (D)

• Measures species richness

• If D is high the area may be a stable ancient site.• Low D may suggest pollution, recent colonization, or

agricultural management

D=N(N-1) S n(n-1)

D=Diversity

N=total number of organisms of all species found

n=number of individuals of a particular species

Random sampling and quadrat methods,

See the worksheet

• Use of a transect • See the worksheet

INTERACTION BETWEEN BIOTIC FACTORS

1- Symbiosisa. Mutualismb. Commensalismc. Parasitism

2- Competition3- Feeding relationship

a. herbivory (grazing)b. predation

Symbiosis: is a long term interaction between two species which live in or on..

• Mutualism describes any relationship between individuals of different species where both individuals benefit.

• lichen: algae and fungi, legumes and nitrogen fixation bacteria

• anemone hermit crab

Mutualism: Lichen

Lichen

Commensalism

• Commensalism describes a relationship between two living organisms where one benefits and the other is not significantly harmed or helped.

Commensalism

Barnacles adhering to the skin of a whale or shell of a

mollusk

Parasitism

• A parasitic relationship is one in which one member of the association benefits while the other is harmed

Feeding relationship

• Producers: produce organic molecules by photosynthesis or chemosynthesis

• Consumers: feed on other organisms.– Herbivores: eat plants. They are primary

consumers– Carnivores: they eat meat. They can be secondary,

tertiary consumers.– Omnivores: they eat both meat and plant.

ScavengersIt is a carnivorous feeding behaviour in which a predator consumes corpses that were killed by by other animals. It is part

of decomposition. Well known scavengers include vultures, burying beetles, blowflies, yellowjackets, and raccoons

Detritivores: Animals which primarily consume dead plants. Organisms such as termits, worms in soil are examples.

Decomposers: fungi and bacteria that obtain their nutrients and energy mainly by feeding on dead organisms by digesting them outside of the cell.

Feeding relationship

Prey- predation

Competition

Interspecific competition:

Competition between two different species.

Why?

• Intraspecific competition: competition between the members of the same species.

• Why do they compete?

NICHE describes; • where the organism lives• how it lives• how it interacts with other member of

the community

WHAT IS NICHE?

Fundamental and Realized Niches

Fundamental niche: is the niche that an organism could potentially occupy.

Realized niches: is the proportion of the fundamental niche that actually occupied by the organisms. In other words it is the actual mode of existence, which results from its adaptations and competition with other species.

The Competitive Exclusion PrincipleKEY POINTS

• For any given species a niche is precise and cannot be occupied by more than one species.

• When the niches of two different species overlap, competition takes place for the resources.

• The stronger species exclude the weaker one

Parasitism: ectoparasite sheep thickMutualism : Fungus takes sugar and amino acids from root and it gives ions to the root

Biomass

Biomass is the total weight (or volume, or energy equivalent) of living organisms in a given area (e.g. a quadrat).

(kJ m−2 yr−1).

Productivity of an ecosystem

• Primary productivity, the production of new organic matter by green plants (autotrophs)6CO2 + 12H2O ----------- C6H12O6 + 6H2O +6O2

Photosynthesis

• Secondary productivity, the production of new organic matter by consumers (heterotrophs).

Both primary and secondary productivity can be divided into gross productivity and net

productivity. 1- Gross productivity is the total gain in organic

matter (biomass) or energy per unit area per unit time.

2- Net productivity is the gain in energy or biomass per unit area per unit time that remains after deduction due to respiration.

Gross production – respiration = net production.

Values are in KJm-2 yr -1

Net Productivity (NP) of Carnivores 12

Respiration and other losses

Z

Consumed by carnivores

Y

Decomposers & other losses 320

NP of herbivores 400

Respiration & other losses

X

Consumed by herbivores W

Decomposers & other losses 32000

NP of Producers 40000

Source: M01 IB Examination

Carnivores

HERBIVORES

PRODUCERS

360,000

400,000

2.00 x 107

1.96 x 107

Calculate W,X,Y and Z

So how are gross and net productivity related ?

Net productivity = Gross productivity - Respiration Energy

or using symbols:

NP = GP - R

This equation applies to animals too, but more on that later…..

The productivity of a plant is called:

PRIMARY PRODUCTIVITY

because plants are the first or primary organisms in the food web

So what about animal productivity?

• Animals must eat other organisms to obtain energy, unlike plants which photosynthesize

• Animals may eat plants or animals or both• Not all the energy in food is absorbed (assimilated) into an

animal’s body• Unassimilated food is ejected as faeces or droppings

So gross productivity = food assimilated or gross productivity = food eaten - energy in faeces

What about net productivity for an animal (secondary consumer)?

• Gross secondary productivity = Energy in eaten food - energy in faeces

• As well as keeping themselves alive, animals must use energy to move and keep warm - plants need rather less energy- but in the end it, as in plants, it all turns to heat

• Net secondary productivity (NSP ) = food eaten - faeces - respiration energy

so NSP = GSP- R (just like plants)

?

NPP versus NSP

PRODUCTIVITY OF ECOSYSTEMS

The following data were collected in a study of secondary productivity in a population of woodlice. Some of the woodlice produced offspring during the experiment.

Source: IB Examination Paper 1 May01

Estimated Dry Mass at start of experiment (g)

Estimated Dry Mass at end of experiment (g)

Adult woodlice 1.53 1.59

Young woodlice - 0.63

Food (dead leaves)

22 19.45

Fecal matter - 0.84

ANSWER

1. What is the Gross Productivity (g) of this population over the period of the experiment?

2. What is the Net Productivity (g) of this population over the period of the experiment?

ANSWER1. What is the Gross Productivity (g) of this

population over the period of the experiment?Answer: GP = Food Eaten – Fecal Loss

GP = (22 - 19.45) – 0.84GP = 1.71

2. What is the Net Productivity (g) of this population over the period of the experiment?

Answer: NP = Biomass (dry mass)NP = 1.59 – 1.53 + 0.63NP = 0.69

DETERMINING PRIMARY PRODUCTIVITY:

THE LIGHT BOTTLE-DARK BOTTLE METHOD

The light bottle-dark bottle method can be used to estimate the rate of photosynthesis, the amount of caloric energy stored in the carbon compounds that are formed.

What does this method measure?

• This method compares the oxygen changes that occur in plankton communities contained in light bottles with those occurring in dark bottles during a specified period of time.

What happens in the light bottle

• In the light bottle, oxygen is being produced during photosynthesis by the phytoplankton in the water and oxygen is being consumed by plant and animal respiration.

What happens in the dark bottle

• In the dark bottle, only respiration is occurring because there is no light present for photosynthesis to occur.

How can we measure the biomass at different trophic levels?

• find the dry mass of a representative sample (at least) of each type of organism by heating weighted sample at 70-80 °C .

• This technique kills many animals which is not ethical. Instead of dry mass measurement method, fresh mass can be used to estimate biomass of the trophic level. It is less accurate.

Ecological productivity by the fresh- water community at Silver Springs, Florida

Biomass expressed in terms of energy content (kJ m–2 yr–1)

Trophic level Matter retained lost respirationExported due

to herbivory or

predation by organisms of

next trophic

level ________________________________________________________________________Producers 169550112 35263Primary consumers 6506 27154

1602Secondary consumers 192 1322

88Tertiary consumer 33 54

Calculate net productivity of the primary consumers by using data above. Gross PP= 35263+50112+1695= 87070 kJm−2yr−1. Net PP= 87070- 50112 = 35263

• The gross production by the primary consumers (herbivores that eat producers – the green plants) was the biomass that is recorded as exported by the primary producers, that is 35 263 kJ m−2 yr−1.

• The respiratory loss by the primary consumers was 27 154 kJ m−2 yr−1. So the net production by the primary consumers was (NSP):

• 35263 − 27154 = 8109kJm−2yr−1.

• Calculate net production by the secondary and the tertiary consumers of the fresh-water community at Silver Springs

SUCCESSION

Succession, a sequence of communities develops with time by a process known as ecological succession.

ORSuccession is the directional and cumulative change in the types of species that occupy a given area through

time.

• Primary succession: When the succession sequence starts on entirely new land without established soil, then the process is known as a primary succession. Ex: at river deltas, at sand dunes, from cooled volcanic lava,

• Secondary succession: A succession that starts from existing soil is known as a secondary succession. Ex: after forest fire, human destruction

Primary succession and secondary succession

Succession

Primary successionSecondary succession

What is the difference between the two?

Succession could be…• Primary

1o Succession

• Primary begins when new territory is formed devoid of life.

• The pioneer species are adapted to life without soil and in the case of lichens, produce it by decomposing rock.

• Plants cannot grow

Succession involves: -colonization, establishment, extinction

• Succession stops when species composition changes no longer occur with time, and this community is said to be a climax community.

Stages• Most successions contain a number of stages that

can be recognized by the collection of species that dominate at that time

• These stages are called seres or seral stages

Succession could be…• Secondary

• Secondary Succession begins when an area is made devoid of vegetation because of a disturbance

• disturbances are fires, wind storms, volcanic eruptions, logging, climate change, etc..

Succession in terrestrial environments

Sourcehttp://www.physicalgeography.net/fundamentals/images/succession.gif

• Intially, Biomass and productivity of the community increases.

• This, in turn, provides food for a larger community of consumers.

• As succession continues, the diversity of species in the community increases.

• As the system approaches its climax, the rate of increase in net productivity of the plants is consumed by its own heterotrophs.

• In a climax community, the system comes into equilibrium and reaches peak energy efficiency.

How does primary succession affect species diversity and production of an ecosystem?

How do living organisms affect abiotic factors during primary succession?

• Role of lichens?• Role of producers?• Role of decomposers?

Major biomes

• desert • grassland • shrubland (chaparral, matorral, maquis and

garigue, dry heathlands, fynbos) • temperate deciduous forest • tropical rainforest • tundra.

PROJECT PRESENTATION

How do rainfall and temperature affect the distribution of biomes?

G3 Impacts of humans on ecosystems Calculate the Simpson diversity index for two local communities.

G.3.1

Analyze the biodiversity of the two local communities using the Simpson index. G.3.2

• http://www.biologycorner.com/flash/mark_recap.swf

Discuss reasons for the conservation of biodiversity using rainforests as an example. G.3.3

• Rainforests cover almost 2% of the Earth’s land surface,

• habitats for almost 50% of all living species.

• It is the case that tropical rainforests contain the greatest diversity of life of any of the world’s biomes. Read page 622-623 and discuss why rainforests should be conserved.

Alien species (introduced species, invasive species)

• Alien species are introduced plants and animals that have been accidentally or deliberately transferred from habitats where they live, to new environments where the abiotic conditions are also suitable for them.

• the rabbit (Oryctolagus sp.)• Japanese knotweed (Fallopia japonica)• American grey squirrel (Sciurus carolinensis)

Discuss the impacts of alien species on ecosystems. G.3.5

• Japanese knotweed (Fallopia japonica) deliberately introduced into northern Europe in the early nineteenth century as an ornamental plant for garden ponds and lakes;

• American grey squirrel (Sciurus carolinensis) accidentally introduced into Britain in the nineteenth century.

•

Outline one example of biological control of invasive species. G.3.6

• the rabbit (Oryctolagus sp.) deliberately introduced from Europe, into Australia, and the myxoma virus disease of rabbits, from South America, introduced as a biological control;

The role of ozone layer

+ UV light + UV light

O2 →O·+O· ⎯⎯⎯⎯⎯ O·+O2 →O3 ⎯⎯⎯⎯⎯

• In the stratosphere, CFCs are exposed to high levels of UV light, and are broken down. Highly reactive chlorine atoms are then released, and these break down ozone molecules in a cyclic reaction:

• O3 + Cl· → ClO + O2 ⎯⎯⎯⎯⎯• ClO + O· → Cl· + O2 ⎯⎯⎯⎯⎯

Physical change: effects of ultraviolet (UV) radiation on living things

• Mutation in all organisms• Skin cancer