4.1 species, communities and ecosystem Flashcards
species
a group of organisms that can interbreed and produce fertile (and viable) offspring.
habitat
the environment within which a species normally lives
population
a group of organisms of the same species who live in the same area at the same time.
community
populations of different species(plants&animals) living and interacting in the same area
ecosystem
a community and its abiotic environment
ecology
the scientific study of the relationship between living organisms and between those organisms and their environments
abiotic factor
non-living components within an ecosystem such as water, soil, and atmosphere
biotic factors
living things within an ecosystem; such as plants, animals, and bacteria.
autotrophs
synthesises its own organic material from simple inorganic substances (CO2, nitrates).
Energy for this process is derived from sunlight (photosynthesis) or via the oxidation of inorganic molecules (chemosynthesis).
as autotrophs synthesise their own organic molecules they are commonly referred to as producers
heterotrophs
- Obtains organic molecules from other organisms (either living / recently killed or their non-living remains and detritus)
- heterotrophs cannot produce their own organic molecules and obtain it from other sources, they are called consumers
mixotrophs
Certain unicellular organisms may on occasion use both forms of nutrition, depending on resource availability.
Euglena gracilis possess chlorophyll for photosynthesis (autotrophic) but may also feed on detritus (heterotrophic).
types of heterotrophs and their differentiation
Detritivores ingest organic molecules found in the non-living remnants of organisms (e.g. detritus, humus)
Saprotrophs release digestive enzymes and then absorb the external products of digestion (decomposers)
Consumers ingest organic material from living or recently killed organisms.
types of autotrophs (not v imps)
photoautotrophs - makes organic compounds using energy derived from the sun
chemoautotrophs - makes organic compounds using energy derived from the oxidation of chemicals
detritivore
Detritivores ingest organic molecules found in the non-living remnants of organisms (e.g. detritus, humus)
saprotrophs
Saprotrophs release digestive enzymes and then absorb the external products of digestion (decomposers)
types of decomposers
detritivores, saprotrophs
(ingest - release digestive enzymes)
nutrients
refer to the material required by an organism, and include elements such as carbon, nitrogen and phosphorus
why is nutrient cycling necessary?
The supply of inorganic nutrients on Earth is finite – new elements cannot simply be created and so are in limited supply. this necessitates nutrient cycling.
how are chemical elements constantly recycled after being used?(organic, inorganic material)
- Autotrophs obtain inorganic nutrients from the air, water and soil and convert them into organic compounds
- Heterotrophs ingest these organic compounds and use them for growth and respiration, releasing inorganic byproducts
- When organisms die, saprotrophs decompose the remains and free inorganic materials into the soil
- The return of inorganic nutrients to the soil ensures the continual supply of raw materials for the autotrophs
mesocosm
Mesocosms are enclosed environments that allow a small part of a natural environment to be observed under controlled conditions
if two species are typically found within the same habitat, they show a…… they have a ______relationship
positive association
Species that show a positive association include those that exhibit predator-prey or symbiotic relationships
if two species are tend not to occur within the same habitat, they show a…… they have a ______relationship
negative association.
competitive relationship where they compete for the same resources.
One species may utilise the resources more efficiently, precluding survival of the other species (competitive exclusion)
Both species may alter their use of the environment to avoid direct competition (resource partitioning)
If two species do not interact,
there will be no association between them and their distribution will be independent of one another
quadrant sampling
is used to determine the presence of two species within a given environment.
what is a quadrat and how is it used?
- A quadrat is a rectangular frame of known dimensions that can be used to establish population densities
- Quadrats are placed inside a defined area in either a random arrangement or according to a design (e.g. belted transect)
- The number of individuals of a given species is either counted or estimated via percentage coverage
- The sampling process is repeated many times in order to gain a representative data set
limitation of quadrat sampling
Quadrat sampling is not an effective method for counting motile(capable of movement) organisms – it is used for counting plants and sessile(immobile) animals
chi-squared test purpose
A chi-squared test can be applied to data generated from quadrat sampling to determine if there is a statistically significant association between the distribution of two species
how to conduct chi-squared test
- Identify hypotheses (null versus alternative)
- Construct a table of frequencies (observed versus expected)
- Apply the chi-squared formula
- Determine the degree of freedom (df)
- Identify the p value (should be <0.05)
