4.1 Species, Communities, and Ecosystems Flashcards
The continued survival of living organisms including humans depends on sustainable communities.
Species
Group of organisms that can potentially interbreed to produce fertile, viable offspring.
Hybrids
Offspring produced by crossbreeding, reproductively sterile. E.g. Liger, mule.
Population
Group of organisms of the same species that are living in the same area at the same time.
EXTRA: Organisms that live in different populations are reproductively isolated and unlikely to interbreed, however, if interbreeding is functionally possible these organisms are classified as the same species.
Community
Groups of populations that live and interact with each other in a given area
Habitat
The environment in which a species usually lives, or the location of a living organism.
Ecosystem
A community and the abiotic environment.
Ecology
The study of relations between organisms as well as their environment
Autotrophs
Producers - synthesis own organic molecules from simple inorganic substances - e.g. CO2, nitrates.
Energy for synthesis is derived from sunlight (photosynthesis) or oxidation of inorganic molecules (chemosynthesis)
How is energy for synthesis is derived for Autotrophs
From sunlight (photosynthesis) or oxidation of inorganic molecules (chemosynthesis)
Heterotrophs
consumers - obtain organic molecules from other organisms as they cannot produce their own organic molecules
Name 3 different heterotrophs
- Consumers
- Detritivores
- Saprotrophs
Mixotrophs
Unicellular organisms that can use both forms of nutrition, depending on resources availability
Example of mixotroph
Euglena gracilis
- chlorophyll for photosynthesis (autotrophic)
- feeds on detritus (heterotrophic)
Consumers
ingest organic molecules found from living/recently killed organisms.
- herbivores: cows.
- carnivores: tiger.
- Omnivores: humans, pandas
Detritivores
ingest organic molecules found in the non-living remnants of organisms, e.g. detritus, humus, through internal digestion.
- dung beetles
- earthworms
- snails
- crabs
Saptrotrophs
Organisms that live on/in non-living organic matter, secreting digestive enzymes to facilitate external digestion of nutrients. As saprotrophs facilitate the breakdown of dead organic material, they are commonly referred to as decomposers.
- Bacteri
- fungi
- mushrooms
- mold.
Detritus
dead, particulate organic matter, e.g. decaying organic material and feces
Humus
decaying lead litter intermixed within the topsoil
Nutrients
Materials required by an organism - carbon, nitrogen, phosphorus.
As the supply of inorganic nutrients on Earth is finite, thus there is a limited supply as new elements cannot simply be created. Hence, chemical elements are constantly recycled
Nutrient cycle
- Autotrophs – synthesise inorganic nutrients into organic compounds.
- Heterotrophs – ingest organic compounds from autotrophs for growth and respiration, releasing inorganic by-products.
- Saprotrophs – decompose the remains of deceased organisms and inorganic material into the soil < ensuring a continual supply of raw materials for the autotrophs.
3 main components required for sustainability in an ecosystem
- energy availability
- nutrient availability
- recycling of wastes
3 main components required for sustainability in an ecosystem (EXPLAINED)
- Energy availability – e.g. light from sun provides initial energy source.
- Nutrient availability – saprotrophic decomposers ensure consistent recycling.
- Recycling of wastes – certain bacteria can detoxify harmful waste by-products, e.g. Nitrosomonas.
What are mesocosms?
Enclosed environments that allow parts of a natural environment to be observed under controlled conditions.
E.G. Terrarium – a small transparent container where selected plants are observed.
Quadrant sampling
A quadrat is a rectangular frame of known dimensions that can be used to establish population densities – placed inside a defined area in either random or according to a design. Not an effective method for counting motile organisms, mainly used for plants and sessile animals.
Chi-squared tests
Can be applied to data generated from quadrat sampling to determine if there is a statistically significant association between the distribution of two species, at the 0.05 level.
(observed value - expected value)^2 / expected value = x^2
0 association
there is no potential interaction between species in a given environment as they are independent of one another.
+ association
typically found within the same habitat.
POSSITIVE ASSOCIATION: Predator-prey or symbiotic relationship.
- association
typically do not occur within the same habitat
NEGATIVE ASSOCIATION: competition for the same resources
- competitive exclusion
- resource partitioning
Competitive exclusion
1 species may utilise the resources more efficiently, precluding survival of the other species.
Resource partitioning
both species alter use of the environment to avoid direct competition.