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Posted on Nov 19, 2020 in Language

COMMUNITIES AND ECOSYSTEMS:

Definitions:

  • Species: a group of organisms that can interbreed and produce fertile offspring
  • Habitat: environment in which a species normally lives or the location of a living organism
  • Population: group of organisms of the same species that love in the same area at the same time
  • Community: a group of populations living and interacting with each other in an area
  • Ecosystem: a community and its abiotic environment
  • Ecology: the study of the relationships between living organisms and between organisms and their environment
  • Environment: biotic and abiotic factors that affect an organism
  • Autotroph: an organism that synthesizes its food from inorganic substances  plants, bacteria
  • Heterotroph:san organism that obtains its food from other organisms
    • Exception: plants and algae being parasitic  Dodder plant
  • Consumer: organism that ingests by internal digestion other organic matter that is living or recently killed
  • Detritivore: organism that ingests dead organic matter  earthworms
  • Saprotroph: organisms that ingest by external digestion dead organic matter  bacteria
  • Food chain: shows who eats who – arrow represent the flow of energy – start with producers
    • Diatoms – zooplankton – Mussels – Cod – Orca
  • Food web: shows interactions between different food chains
  • Trophic level: level of feeding in a food chain
    • First level: producers
    • Second level: herbivores or primary consumers
    • Third level: secondary consumers
    • Fourth level: tertiary consumers
  • Mesocosm: small experimental area set up for ecological experiments
  • Species association: relationship between two species
    • Positive association: usually found together
    • Negative association: usually found apart
    • Interdependent

Can populations live in isolation:

  • They can’t because they depend on interactions and relationships with many other species for long-term survival

Do organisms interact with their abiotic environment:

  • Organisms do not need each other
  • They need inorganic nutrients (abiotic environment)
  • Abiotic factors can influence success of organisms

How does the movement of nutrients through food chains compare to energy

  • Energy enters and leaves ecosystems
  • Nutrients (carbon, nitrogen) are recycled in ecosystems

Role of saprophytes in ecosystems

  • Thanks to their extracellular digestion, they release nutrients back into the soil or atmosphere
  • Plants use them for their growth
  • Called decomposers

What do ecosystems need to be sustainable

  • Nutrient availability: decomposers recycle inorganic nutrients making nutrients constantly available
  • Detoxification of waste products: waste from one organism is food for another
  • Energy availability: thanks to the sun supply

ENERGY FLOWS

  • Food chain: model showing who eats who
  • Biomass: total mass of group if organisms
    • It decreases as you move along the food chain
  • Pyramid of numbers and biomass: producers are placed at the bottom
  • Pyramid of energy: shows the flow of energy from one trophic to the next one

Original source of energy for food

  • The sun provides energy for food chains
  • Autotrophs fix the sun’s energy in photosynthesis (light into chemical energy)

Energy flow through food chains

  • Energy enters the food chain by producers fixing light energy into chemical energy
  • Energy flows through food chains as organisms are consumed
  • Energy is lost between trophic level as some material is not consumed, and as heat loss though cell respiration

How efficient are energy transfers?

  • They leave 10% of the energy for transfer to the next trophic level (they consume about 90% from just staying alive)

What happens to the waste energy?

  • The waste energy is released from respiration and cannot be used by organisms  disappears into the atmosphere

Why are food chains short?

  • Because of the loss of energy at each trophic level
  • Not enough energy left

CARBON CYCLING:

Autotrophs with carbon dioxide:

  • They can absorb it from the atmosphere and convert it into carbohydrates
    • Called carbon fixation

Carbon dioxide in water:

  • It dissolves in water
  • It also combines with water to form carbonic acid
    • Water becomes acidic

Why do carbon dioxide levels change?

  • When there is light  autotrophs absorb CO2 in photosynthesis (decreases)
  • When there is no light  animals and plants release CO2 from respiration (increases)

Methanogenesis: the production of methane gas by anaerobic respiration from organic matter

  • It happens in anaerobic environments (muddy shores or in the lakebeds)
  • Carried out by methanogens

What is peat and how does it form?

  • A dark compressed acidic material from incomplete breakdown or organic matter

What is coal and why does it form

  • Coal is fossilized peat that formed under pressure of sediments.
  • Compression and heat turn peat into coal

Oil and natural gas: they form in the mud at the bottom of sea and lakes under anaerobic conditions and pressure

What is combustion and what does it do to carbon dioxide levels:

  • When burning hydrocarbon fuels, carbon dioxide is released into the air

What is limestone and how does it form

  • Molluscs deposit carbon in their shells
  • These parts resist decay after death
  • When they settle, they form limestone rock

Carbon cycle:

What are fluxes and pools:

  • Pool: a reserve of an element  CO2 is an inorganic pool of carbon
  • Flux: the transfer of an element from one pool to another (shown as an arrow)  plants absorb CO2 from the atmosphere in photosynthesis, turning it into sugars

Evidence for evolution

  • Evolution: change in heritable characteristics of a population over time

Difference between heritable and acquired characteristics

  • Acquired characteristics: they develop during lifetime and are not inherited
  • Heritable characteristics: passed from parent to offspring

Phylogeny: evolutionary relationships (family tree diagram)

Fossils and how can they indicate time:

  • Fossils: can be casts, imprints, organisms trapped or petrified organisms
    • They can be radioisotope tested for age
  • Provide evidence:
    • Show that species were not the same as the ones now, but they have similarities  suggests change over time
    • Show that there has been change, and the order in which they find the fossils matches the sequence  bony fish – amphibians – reptiles – mammals

Homologous structures providing evidence for evolution:

  • When anatomies of different species are compared, many similarities can be found  common ancestor
  • The similar structures are called homologous structures  vertebrate pentadactyl limb

Analogous structures: superficial similarities in structure  body shape of fish and dolphins

Vestigial organs: inherited traces of organs that they no longer need  show common ancestor.

Selective breeding of domesticated animals providing evidence for evolution: