Topic 4: Ecology Flashcards
What is a species?
A group of organisms that can potentially interbreed to produce fertile, viable offspring
Members of a single species are unable to produce fertile, viable offspring with members from a different species
What is a population?
a group of organisms from the same species that are living in the same area at the same time.
What is a community?
a group of populations living together and interacting with each other within a given area
What is an ecosystem?
a community and its abiotic environment
What is ecology?
the study of the relationship between living organisms, or between living organisms and their environment
Distinguish between an autotroph, heterotroph and mixotroph
Autotrophs/Producers: Synthesizes its own organic molecules from simple inorganic substances (e.g. CO2, nitrates)
Energy for this process is derived from sunlight (photosynthesis) or via the oxidation of inorganic molecules (chemosynthesis)
Because autotrophs synthesize their own organic molecules they are commonly referred to as producers
Heterotrophs/Consumers: Obtains organic molecules from other organisms (either living / recently killed or their non-living remains and detritus)
Because heterotrophs cannot produce their own organic molecules and obtain it from other sources, they are called consumers
Autotrophs obtain the simple inorganic substances required for this process from the abiotic environment:
These nutrients – including carbon, nitrogen, hydrogen, oxygen and phosphorus – are obtained from the air, water and soil
Mixotrophs: can have both auto/heterotrophic tendencies depending on environmental circumstance. Organisms such as Euglena gracillis can photosynthesis but also feed on detritus that they ingest by endocytosis.
Types of heterotrophs/consumers
- consumers feed on living organisms by digestion: herbivores, carnivores, omnivores
-scavengers: a type of consumer that principally feed on dead and decaying carcasses rather than hunting live prey (hyenas, vultures and carrion birds (such as crows))
-detritivores: a type of heterotroph that obtains nutrients from non-living organic sources, such as detritus and humus. (dung beetles, earthworms, woodlice, snails and crabs)
-saprotrophs/decomposers: live on (or in) non-living organic matter, secrete digestive enzymes into it and absorbing the products of digestion, do not ingest food but use enzymatic secretion to facilitate external digestion (bacteria and fungi)
Explain Nutrient Cycling?
-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
Process of chi-squared/quadrant sampling:
● Base line marked around habitat using measuring tape.
● Random numbers are generated using a number generator.
● First number is used to determine distance along the measuring tape.
● Second is used to determine a distance out across the habitat at right angles to the tape.
● Quadrant is placed precisely at the distance determined by the two random numbers.
● Only suitable for immotile species.
Results:
o Positive associations: two species occur in the same parts of a habitat and are therefore associated.
o Negative associations: two species occur in different parts of a habitat thus tend to not grow around each other and are therefore associated.
o Independent distribution: no association between species (forms null hypothesis during chi squared test).
What is photosynthesis?
All green plants, and some bacteria, are photoautotrophic – they use sunlight as a source of energy
Light energy is absorbed by photoautotrophs and is converted into chemical energy via photosynthesis
-This light energy is used to make organic compounds (e.g. sugars) from inorganic sources (e.g. CO2)
-Heterotrophs ingest these organic compounds in order to derive their chemical energy (ATP)
-When organic compounds are broken down via cell respiration, ATP is produced to fuel metabolic processes
What is a trophic level?
The position an organism occupies within a feeding sequence is known as a trophic level
Trophic level 1: producer
Trophic level 2: primary consumer
Trophic level 3: secondary consumer
Trophic level 4: tertiary consumer
What do the arrows in a food chain represent?
they represent the transfer of energy and matter as one organism is eaten by another
How is energy released from organisms and what is produced from this released energy?
It is realized by cell respiration and produces ATP
-ATP is then used to fuel metabolic reactions required for growth and homeostasis
-A by-product of these chemical reactions is heat (thermal energy), which is released from the organism
Some energy is also lost by:
-Being excreted as part of the organism’s faeces
-Remaining unconsumed as the uneaten portions of the food
Chemical energy produced by an organism can be converted into these 3 forms:
-Kinetic energy (e.g. during muscular contractions)
-Electrical energy (e.g. during the transmission of nerve impulses)
-Light energy (e.g. producing bioluminescence)
All of these reactions are exothermic and release thermal energy (heat) as a by-product
-Living organisms cannot turn this heat into other forms of usable energy
-This heat energy is released from the organism and is lost from the ecosystem (unlike nutrients, which are recycled)
-Hence ecosystems require a continuous influx of energy from an external source (such as the sun)
How much energy is lost between trophic level?
Most of the energy is lost to the organism – either used in respiration, released as heat, excreted in faeces or unconsumed
Typically energy transformations are ~10% efficient, with about 90% of available energy lost between trophic levels
The amount of energy transferred depends on how efficiently organisms can capture and use energy (usually between 5 – 20%)
What is biomass?
Biomass is the total mass of a group of organisms – consisting of the carbon compounds contained in the cells and tissues
As energy is lost between trophic levels, higher trophic levels store less energy as carbon compounds and so have less biomass
Biomass diminishes along food chains with the loss of carbon dioxide, water and waste products (e.g. urea) to the environment
-Higher trophic levels receive less energy / biomass from feeding and so need to eat larger quantities to obtain sufficient amounts
-Because higher trophic levels need to eat more, they expend more energy (and biomass) hunting for food
-If the energy required to hunt food exceeds the energy available from the food eaten, the trophic level becomes unviable
