Ecology Flashcards
Define ecology
The study of the relationship of living organisms with each other, and the environment
Define population
A group of organisms of the same species occupying the same area at a given time
Define community
A group of organisms of different species living in a given area at a given time
What is an ecosystem?
A biological unit consisting of biotic and abiotic factors interacting with each other
What is a biosphere?
Any part of the earth occupied by living things
(Divided into aquatic and terrestrial)
What is a biome?
A region of the biosphere with a definite climate and organisms
What is a habitat?
A specific locality in the biome where an organism lives
Define the term ‘biological niche’
This is the role and position that a species has within its habitat
Distinguish between realized niche and fundamental niche
Realized niche is the actual space an organism inhabits and the resources it can access as a result of limiting pressure from other species.
- It occurs in the presence of predators, competitors and parasites; limiting their habitat and roles performed by an organism (it is smaller in size)
While fundamental niche is the entire set of conditions under which animal can survive and reproduce itself
- It occurs in the absence of predators, competitors and parasites, allowing an organism experience, a larger habitat, and perform a variety of roles
Define abiotic factors
These are nonliving factors in an ecosystem or environment
What are biotic factors?
These are the living things in an ecosystem
What are producers?
These are organisms that can synthesize their own food
Define Consumers
These are animals that feed on plants or other animals
Consumers that feed exclusively on plants are called?
Primary consumers or herbivores
Consumers that feed on herbivores are called?
Secondary consumers
Consumers that feed on
both primary and secondary consumers are called?
Tertiary consumers
What are decomposers?
These are organisms that feed on dead organic matter (DOM)
What is the difference between detritivores and decomposers.
Detritivores are usually macro organisms, and start the decomposition process
Decomposers are micro organisms that complete the process of decomposition
What is the importance of consumers?
- They regulate population of plants
- They release carbon dioxide gas, which plants use to make their own food
- Decomposition of dead consumers provides nutrients to the soil
- Lower consumers provide food to higher consumers
- They regulate the population of other animals
What is the importance of decomposers?
- They recycle nutrients by feeding on DOM
- Some decomposers like mushrooms, are a source of food to some animals
- They provide carbon dioxide to green plants
- They unlock the trapped energy in the body of dead organisms
What is the principal source of energy?
The sun
Why do autotrophs only trap about 1% of the total energy available from the sun?
- Part of the light cannot be used or captured by their pigments
- Sunlight energy is trapped by the ozone layer
- Some energy is converted into heat before reaching the plants
- Some energy is reflected by dust, particles, clouds, surfaces, vegetation, water, etc
- Some energy is used in evaporation and transpiration
What is primary productivity?
This is the amount of energy and organic matter stored in primary producers per unit area per unit time
What factors affect primary productivity?
- Temperature
- carbon dioxide
- Light intensity
- Amount of water available
Define a food chain
This is a linear flow of energy from one trophic level to another
What is a food web?
A complex nutritional interrelationship that illustrates alternative food sources, and predators for each organism
What is an ecological pyramid?
These are histograms that provide information about feeding levels in Ecosystems
What is the pyramid of numbers?
This is a histogram, representing the number of different organisms at each trophic level in an ecosystem at any one time
Give the limitations of the pyramid of numbers
-Drawing the pyramid, accurately to scale may be difficult
- The pyramid may be inverted
- The tropic level of an organism may be difficult to ascertain
- The young forms of species may have a different diet from adults
What is the pyramid of Biomass?
This is a histogram showing the total dry mass of organisms present at each feeding level
Give disadvantages of the pyramid of biomass
- Does not account for the rate of production
- It may also be inverted
What is the pyramid of energy flow?
It is a histogram showing the total amount of energy present at each feeding level
Give the advantages of the pyramid of energy flow
- It can never be inverted
- It accounts for the rate of production
- Allows comparison of ecosystems
What are the disadvantages of pyramids of energy?
-Difficult to obtain data.
-The organisms are killed.
What are the general problems of ecological pyramids?
- They may not always indicate the actual trophic level
-They always omit decomposers - Not every part of the organism is edible
Define trophic efficiency
This is the percentage of energy at one trophic level that is converted into organic substances at the next trophic level.
Why is the transfer of food from producers to primary consumers the lowest?
- Plants contain cellulose which many animals cannot digest, because they lack cellulase enzyme
- Some energy is lost in respiration
- energy is lost in form of excretion
-Some parts of the plants are indigestible - some parts are unpalatable
- some parts cannot be accessed eg roots
What are the adaptations of herbivores to feeding on plants?
- They chew cud, which increases on the breakdown of plant material.
- Some herbivores have symbiotic bacteria.
-They have very many large, molars and premolars, which increases the surface area for grinding. - Some have a four chambered stomach increasing on surface area for digestion.
- They have a long elementary canal to increase the surface area for digestion.
Why is the Trophic efficiency from primary consumers to secondary consumers higher?
- Animal bodies have a lot of proteins, which are easier to digest by proteases
- The faeces contain much less undigested matter
Why is in Trophic efficiency From primary consumers to secondary consumers not still 100%?
- Some energy is lost through respiration
- Some energy is lost through excretion
- Some parts are not edible.
- Some energy is lost through egestion
Why doesn’t the length of the food chain exceed five trophic levels?
Because the number of organisms decreases at each successive feeding level, and the energy left in organisms is too little to support the large numbers of consumers
What is gross productivity?
This is the total amount of energy and organic matter, stored in an organism over a period of time
What is Net productivity?
This is the amount of energy and organic matter, stored in an organism, and passed on to the next trophic level
What is gross primary productivity?
This is the total rate at which autotrophs synthesize organic matter per unit area per unit time
What is net primary productivity?
This is the amount of energy transferred from primary producers to primary consumers per unit time
True or false
Net primary productivity is equal to gross primary productivity minus respiration and metabolism
True
What is the nitrogen cycle?
This is the saturation of nitrogen in an ecosystem from one part to another
Describe the carbon cycle
- In the nonliving environment, carbon is present as carbon dioxide In the air and dissolved in water; carbonates in rocks and carbon in fossil fuels
FIXATION
- The carbon in fossil fuels, and that in carbonates is not available until it is burnt or chemically changed
- The carbon present in carbon dioxide is the basic source which enters the organism through photosynthesis by plants, and then into various organisms through the food chain
RELEASE BACK INTO THE ENVIRONMENT
- Released as carbon dioxide during respiration in organisms
- By decomposition of dead bodies and body waste by microorganisms.
- By burning of wood and fossil fuel’s.
- By the solution of carbonate rocks.
- By volcanic activity of rocks.
What human activities affect the carbon cycle?
- Cutting trees and plants that absorb CO2.
-Burning of fossil fuels.
-Afforestation and reforestation
Describe the nitrogen cycle
FIXATION
- The atmosphere has 79% nitrogen but this cannot be taken up by organisms unless fixed
- Nitrogen in soil, reduced to ammonium ions, catalyzed by nitrogen fixing bacteria, which may be free living for example Azotobacter or symbiotic bacteria in root nodules such as Rhizobia bacteria
- Lightning causes atmospheric nitrogen and oxygen to react, and produce oxides of nitrogen which dissolve in rainwater fall to the ground as weakly acidic solutions
- Industrial fixation by chemical fertilizer factories using the Haber process
NITRIFICATION
- Ammonium compounds in the soil are converted first to nitrate ions (highly toxic to plants) by nitrosomonas bacteria, and later to nitrate ions by nitrobacter
AMMONIFICATION/ PUTREFACTION
- Decomposers, such as saprophytic, bacteria and fungi, convert nitrogen, rich organic compounds such as urea into ammonia and ammonium containing salts
ASSIMILATION
- Inorganic ammonia, ammonium, and nitrate ions are absorbed by plant roots to make nucleic acids, amino acids and proteins.
- When animals eat plants, the proteins are converted into animal proteins.
DENITRIFICATION
- Pseudomonas denitrificans convert ammonia and ammonium ions back into nitrates and nitrates ions, then into molecular, nitrogen and oxygen