Topic 2 - Biomes

Biomes

a collection of ecosystems sharing similar climatic conditions

What are the 6 biomes

1. Aquatic (marine)

2. Aquatic (freshwater)

3. Deserts

4. Forests (tropica, temperate, boreal)

5. Grassland (tropical, savanna, temperate)

6. Tundra (arctic, alpine)

Characteristics of biomes

1. limiting factors

2. biodiversity

What is insolation

Amount of solar radiation received on a given surface in a given time period

What are the limiting factors

• temperature - enzymes (speeds up biological reactions)

• insolation- photosynthesis

• precipitation

What is the P/E ratio

Precipitation to evaporation ratio
- closer P/E value is to 1 = more rich and fertile the soil

What is the tricellular model of atmospheric circulation

Explains biome distributions by differences in air pressure and corresponding wind which leads to differing precipitations at different latitudes

What is the polar cell like

Rainfall is high at 60º north and south

What is the ferrel cell like

Rainfall is low at 30º north and south

What is the hadley cell like

Rainfall is high at equator

Why is rainfall high at the equator?

• Air in Hadley cell is warm and unstable

• Insolation at the equator is high

• Hot air rises which create the Hadley cell

• Hot air cools creating clouds when risen, leading to heavy tropical rainfall

• Pressure at the equator i low because warm air is rising

Why is rainfall low at 30º?

• Warm air in Hadley cell cools as it moves away from the equator and meets the Ferrel cell

• Low rainfall because cool air comes from poles and sinks at 30º North and south

• Pressure is high and air is dry

• Desert biomes form

Why is rainfall high at 60º?

• warmer winds continue to move towards poles and hit colder polar wind at 60º

• warmer air rises as less dense

• pressure is low

  • air cools into clouds and rains

What is the impact on living organisms from the atmospheric circulations?

1. Species move to keep cool - towards the poles or higher up in mountains

2. Species move to find water - towards the equator

   • Animals can migrate long distances

   • Plants migrate through seed dispersal (much slow process)

   • Geographical barriers such as mountain ranges can prevent movement in both and can lead to extinction

Species

a group of organisms with similar physiology which can interbreed to produce fertile offspring

Habitat

the environment where a species liveP

Population

a group of organisms of the same species which live in the same place at the same time

Ecosystem

self contained system which includes all organisms and their environment interacting with each other and the way in which everything interacts within it

Community

the place in where all species are at one time

Niche

the position occupied by an organism in particular ecosystem, dependent upon the resources it uses

Taxonomy

organisms grouped into taxa according to evolutionary origins and relationships

What is the order of taxonomy

3 domains, kingdoms, phylum, class, order, family, genus, species

Natality and mortality

Natality: birth rate
Mortality: death rate

How to write a name of a living organism?

Genus and species name
Capital letter for genus, lower case for species (underline it)
Eg. Meriones unguiculatus (gerbils)

What are some biotic factors and how does it affect population?

• Competition (decreases)

• Pathogens (decreases)

• Mutualism (increases)

• Parasites (decreases)

• Predation (decreases)

• Herbivory (decrease for plants, increase for animals)

Carrying capacity (K)

the maximum population size of a species which the ecosystem can maintain

Intraspecific competition

Competition within the same species, has great effects on population size and affects natural selection

Interspecific competition

Competition with different species for same resources when niches overlap, resource is less so carrying capacity drops, there is less energy for growth and reproduction
Less well adapted species likely to be out-competed in the long run

What is the J curve (R strategist)

• population curves that represent exponential growth (species that can grow rapidly)

• population is not controlled by limiting factors

• overshoot when population shoots over K

• die-back when population collapses below K

What is the S curve (K strategist)

• population curve that represents logical growth (species that have slow rising population)

• 4 phases: lag, EG, transitional, stationery

What are the characteristics of life?

Movement, respiration, sensitivity, growth, reproduction, excretion, nutrition

What is the compensation point?

Where the rate of respiration is the same as the rate of photosynthesis

Zonation

how the ecosystem changes along a environmental gradient

how do environments differ from top and bottom of a mountain?

temperature, precipitation, solar insolation, soil type, species interaction

biosphere

part of the earth containing life from the upper atmosphere to the deepest ocean

zonation vs succession

zonation: special, static, caused by abiotic factors
succession: dynamic, temporal, caused by progressive changes through time (abiotic that reuslts in biotic changes)

primary succession

colonisation of newly created land by organism

colonisation stage

species called pioneers colonise the area and is adapted to extreme conditions, usually r-selected species

what happens to soil as stages move forward?

simple soil starts from windblown dust and mineral particles, becomes enriched with nutrients from weathering

stages of succession

colonisation: pioneer species colonise, adapted to extreme conditions
establishment: species diversity increasing, invertebrate species visit, increase humus content in soil and water holding capacity
competition: microclimate changes as new species colonise, k species established, early pioneer r species unable to compete and lost in the community
stabilisation: few species colonise as late colonisers become established, complex food webs develop, k species have narrower niches

final stage of succession

climax community - stable and self-perpetuating, exists in a steady state dynamic equilibrium, represents maximum possible development that community can reach under the conditions

properties of pioneer species

• can cope with harsh conditions

• can grow quickly

• make their own nitrogen (eg. nitrogen fixtation in legumes)

  • spreads seeds fast and for long distances

when is biodiversity the highest in succession

during mid-succession stage where there is lots of competition for success

hydrosere

sucession in water

secondary succession

land that already had life on it but was stripped, happens quicker due to seeds in soil previously, soil quality may not be bad but wiped out eg. from a fire or flood

when are abiotic factors the most harsh in succession

in the beginning

when is competition the limiting factor affecting population in succession?

towards the end with less hostile conditions, with high biodiversity and many species

how does GPP and NPP change in sere stages?

early stages: low GPP (from low producers/harsh abiotic conditions), high NPP (energy lost), little increase in biomass
middle stages: high GPP (max. level from highest biodiversity level), increased photosynthesis, increased biomass
late stages: NPP to R ratio is roughly equal (NPP drops as energy used in respiration increase with size), trees meet maximum size

sub climax community

When succession may be prevented by an abiotic factor eg. Waterlogged soil, or a biotic factor such as sheep grazing

plagioclimax

When climax communities are effected by natural events like fire or floods which prevent succession as it increases productivity:respiration ratio

carbon fixtation

when carbon is locked into compounds
- conversion of carbon dioxide to organic molecules through autotrophs

how does photosynthesis ‘fix’ carbon

converts from an inorganic source to an organic source (glucose)

how are fossil fuels formed?

if dead matter fails to decompose, it turns into fossils

examples of organic/inorganic carbon in the system

organic: organisms biomass, fossil fuels
inorganic: sedimentary rock, soil, co2

carbon budget

the amount of carbon dioxide released in a 5 year period

saprobiont

organisms that feed on remains of dead organisms and their waste product

nitrogen fixtation

converting nitrogen to ammonia by rhizobium bacteria for further nitrification

what plants can do nitrogen fixtation?

legumes - has symbiotic relationship with rhizobium which are on their roots, which converts nitrogen to ammonia which can be used by the plant

ammonification

dead organic matter which takes nitrogen into soil in form of organic nitrogen or urea into ammonia by soil bacteria

what is needed in soil to convert ammonium to nitrate to nitrite?

oxygen and soil

why is leaching of nitrites a problem?

causes eutrophication

autotroph

making organic compounds from inorganic compounds

heterotroph

feeds on other organisms to gain energy and make organic compounds

gross primary product GPP

chemical energy store in a plant’s biomass in a given area or volume, the energy converted by plants

net primary production NPP

energy used to stay alive (respiration), and rest passed on in food chain in biomass

how to calculate NPP

NPP = GPP - respiration

net secondary production NSP

total gain in energy or biomass per area per unit time by consumers after allowing for los due to respiration

how to calculate NSP

NSP = GSP - respiration - egestion

assimilation

how much biomass from previous stage can be absorbed into the animals body

how to calculate efficiency of assimilation for an organism

(gross productivity*100)/food eaten

biomass productivity

how much assimilated material is turned into new biomass

how to calculate efficiency of biomass productivity

(net productivity*100)/gross productivity

chemosynthesis

extremophile that start from bacteria, uses chemicals from volcanoes as an energy source to generate organic matter, bacteria are producers at bottom of the ocean that allow ecosystems to thrive.

aerobic respiration equation

glucose + oxygen → carbon dioxide + water

photosynthesis equation

water + carbon dioxide → glucose + oxygen

compensation point

light intensity where photosynthesis = respiration

pyramid of numbers (pros and cons)

pyramid showing number of organisms at each trophic level at one time
pros: simple, allows comparisons over time
cons: doesn’t account for size, juveniles, large populations may not be represented with accurate scale

pyramid of biomass (pros and cons)

shows biomass of all organisms at each trophic level at one time
pros: overcome pyramid of number issues
cons: must kill organisms to measure biomass, samples only, time of year has an impact, doesn’t take into account how long it takes to make biomass

pyramid of productivity (pros and cons)

shows rate of energy or biomass through trophic levels during a fixed time period
pros: over prolonged time period, never inverted, solar radiation is added, most accurate method (shows actual amounts)
cons: energy data is difficult to collect, rare that species only eat one food

differences between r strategy and k strategy

	r strategy	k strategy
life span	short	long
number of offspring	many	few
onset of maturity	early	late
parental care	small	large
reproduction	once in lifetime	>1 in lifetime
type of environment	unstable	stable