ESS chap.2 Ecosystems and ecology

Species

a group of organisms that interbreed and are capable of producing fertile descendants

Population

a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding

Habitat

the environment in which a species normally lives

Niche

• set of biotic and abiotic conditions/resources to which an organism responds

• specific to a species

  2 types:

• fundamental niche: where and how an organism could live

• realised niche: where and how an organism does live

Abiotic and biotic factors

Abiotic: non-living factor that influences an organism/ecosystem (temperature, sunlight, pH)

Biotic: living part of an ecosystem that influences an organism/ecosystem

Population interactions

- Competition:
intraspecific (same species)
-> affect the carrying capacity (max number of a species for a given environment)
interspecific (different species)
-Parasitism:
the parasite benefits from the host
-Diseases
-Mutualism: symbiosis
-Predation:
lower the carrying capacity of both prey and predator
-Herbivory
more plants=higher carrying capacity
=biotic factors

J- population curve

- shows exponential growth
1. initially slow growth
2. become increasingly rapid
- no limiting factors
- after peak value -> population crash (caused by abiotic factors)

Biosphere

part of the Earth inhabited by organisms

Ecosystem

community + physical environment with which it interacts

Community

a group of populations living and interacting with each other in a common habitat (biotic component)

Respiration

• the conversion of organic matter into carbon dioxide and water in all living organisms, releasing energy.

• can be aerobic (requires oxygen) or anaerobic (no oxygen)

• glucose + oxygen -> energy + water + carbon dioxide

• C6H12O6 + 6CO2 -> Energy + 6H2O + 6CO2

Photosynthesis

• the process by which green plants make their own glucose from water and carbon dioxide using energy from sunlight.

• happens in the chloroplasts

• carbon dioxide + water -> glucose + oxygen

• 6CO2 + 6H2O -> C6H12O6 + 6O2

Food chains/webs

• to model feeding relationships

• chain (linear), web (complex)

• composed by trophic levels (position an organism occupies in a food chain)

• producer, primary consumer (herbivore), secondary consumer (carnivore), tertiary consumer (top carnivore)

Pyramids of numbers

• number of organisms (producers and consumers) coexisting in an ecosystem

• pros

  • quick overview

  • compare numbers in different seasons

  cons

  • no account taken of size of organisms

Pyramids of biomass

• shows the biological mass at each trophic level

• pros

  • takes into account the size of organisms

  cons

  • have to kill organisms

  • seasonal variation

  • some animals have bone or shell (affects weight)

Pyramids of productivity

• the flow of energy through trophic levels

• always show a decrease in the energy

• pros

  • shows energy over time (rates of production)

  • compare ecosystems easily

  • never an inverted pyramid

  cons

  • collecting data is difficult (bc over time)

  • many species feed at more than one trophic level, which affects results

Bioaccumulation/biomagnification

• increase in toxins within an organism

• increases in toxins along a food chain

Energy transfer/transformation

-solar energy -> chemical energy (biomass) -> transferred between trophic levels -> leaves as heat energy

- ecological efficiency: % energy transferred from one trophic level to the next (only 10%)

-new biomass/energy supplied * 100

Gross vs Net productivity

the total gain in energy or biomass per unit area per unit time (through photosynthesis or absorption)

A gain in energy or biomass per unit area per unit time after respiratory losses

Primary vs Secondary productivity

Gain by producers in energy or biomass per unit area per unit time

Biomass gained by consumers through feeding and absorption measured in units of mass or energy per unit area per unit time

Gross vs Net Primary Productivity

Total gain on energy or biomass per unit area per unit time by photosynthesis in green plants

Gain by producers in energy or biomass per unit area per unit time after respiratory losses

Gross vs Net Secondary Productivity

Total gain by consumers in energy or biomass per unit area per unit time through absorption

Gain by consumers in energy or biomass per unit area per unit time remaining after respiratory losses

Max sustainable yield

• the highest rate of harvesting that does not lead to a reduction in the original natural capital - net productivity

Producers (autotrophs)

• make their own food (glucose) and convert inorganic molecules into organic ones (plants, algae)

• photoautotrophs: sunlight energy -> chemical energy

• chemoautotrophs: chemical energy -> glucose

Consumers (heterotrophs)

• obtain energy, minerals, and nutrients by eating other organisms

Decomposers

Organisms that break down the dead remains of other organisms

Carbon cycle

The organic circulation of carbon from the atmosphere into organisms and back again

Nitrogen cycle

nitrogen - nucleic acid and protein

Gersmehl’s nutrient model: input and output of nutrients

main gas of the atmosphere and fertilizer

Energy flows

one direction - energy loss between trophic levels

ex: food webs, food chains, pyramids

Matter cycles

• Impacts of human activity on the carbon cycle (urbanization, deforestation, agriculture, fossil fuel use)

• Impacts of human activity on the nitrogen cycle (agriculture, deforestation, fossil fuel use, human population growth)

S-population curve

- establishment of a population
1. lag phase: low population numbers
2.exponential growth phase: limiting factors are not restricting the growth
3.transitional phase: limiting factors start to restrict the growth
4. plateau phase: achieved carrying capacity - changes can cause increase or decrease

Succession

how an ecosystem changes over time - natural, gradual changes

primary: begins in a place without any soil (sides of volcanoes, landslides) + starts with the arrival of pioneer species (do not need soil to survive)

secondary: begins in a place that already has soil and was once the home of living organisms (forest after a fire)

Tundra (biome)

• a collection of ecosystems sharing similar climatic conditions

• located above the Arctic Circle (Arctic Tundra) or at high altitude on moungtains (Alpine Tundra) - coldest biome - low precipitations - low biodiversity (low-growing plants and limited animals such as polar bears) - limited productivity (frozen soil)

Tricellular model of atmospheric circulation

Describes the three cells - Hadley, Ferrel, and Polar - that drive global wind patterns and weather systems.

Zonation

changement of an ecosystem over a distance

Climax communitites

more or less stable community of organisms that is in equilibrium with natural environmental conditions (climate) - happens at the end of ecological succession

more productive, complex food webs, negative feedback mechanisms

K-strategists

Species that concentrate their reproductive investment in a small number of offspring, thus increasing their survival rate and adapting them for living in long-term climax communities (s-curve)

example : elephants, people, sequoia trees

r-strategists

species that tend to spread their reproductive investment among a large number of offspring so that they are well adapted to colonise new habitats rapridly and make opportunistic use of short-lived resources (j-curve)

example : mice, rabbits, bacterias

Temperate forest (biome)

• temperatures and light intensity vary with the seasons

• sufficient rainfalls

• seasonal (lose their leaves in winter) and evergreen (thick leaves or needles) trees

• often dominated by one species

• rich shrub layers due to high sunlight amounts (not do dense trees)

• High NPP

Tropical rainforest (biome)

• high rainfall, sunlight, and temperature

• consistent light and temperature: no seasons

• complex structure with =/ layers : emergent trees + low layers

• only 1% of sunlight reaches the floor so nutrient-poor soil because of the dense canopy

• most productivity in the canopy

• very high NPP

Desert (biome)

• low rainfall, high sunlight, very hot temperatures in the daytime and cold at night

• low vegetation, no tall trees

• many plants and animals adapted to desert conditions like cactus

• soil: low water-holding capacity + easy erosion with the wind (low fertility)

• low NPP

Temperate grassland (biome)

• flat areas dominated by grasses and non-woody plants (no trees)

• clear skies, low rainfall, threat of drought

• grasses die in winter but roots survive

• mat of decomposed vegetation that is rich in nutrients

• animals such as kangaroos, antelopes, or coyotes

• examples: north american prairies, pampas in Argentina

• not so very high NPP

Aquatics (biome)

• largest of all the world’s biomes

• water absorbs some light and limits photosynthesis (no ps in deep oceans)

• freshwater may freeze in temperate or polar winters

• NPP and biodiversity: high in tropical coral reefs, very low in deep oceans, and moderate in freshwater

Nutrient cycle