Session 2: Species, Communities, and Ecosystems

Question 1

What is a species?

Answer 1

Species are animals with genetic similarity and can mate to produce fertile offspring.

Question 2

What is an ecosystem?

Answer 2

Everything that is living or non-living in one area at the same time. It is also a community interacting with the abiotic factors found in its environment

Question 3

What are the two types of autotrophs?

Answer 3

Photoautotrophs which use photosynthesis and chemoautotrophs which use inorganic stuff from Earth’s core (e.g. bottom of the ocean, hydrothermal vents)

Question 4

What are saprotrophs?

Answer 4

Fungi, starfish, etc. which don’t move around –> they grow on their food instead of searching for it.

Question 5

What is competitive exclusion principle?

Answer 5

When niches overlap for different species and the two compete until one starts to decline or is forced to adapt.

Question 6

What are the exceptions to the species definition?

Answer 6

Bacteria produce asexually, and there are species which are very similar but they have slight variation because of where they live –> these species can successfully breed but are considered separate species.

Question 7

What are populations?

Answer 7

all organisms of a certain species which live in a particular area

Question 8

What are communities?

Answer 8

populations of different species living together and interacting

Question 9

Define biotic and abiotic and give examples.

Answer 9

Biotic: living: plants, animals, bacteria

Abiotic: non-living: climate (temperature, rainfall, humidity), soil nutrients (pH, minerals), light, wind/air, and salinity.

Question 10

What are the two main modes of nutrition? Define them.

Answer 10

Autotrophic and heterotrophic. Autotrophs are organisms which can synthesise organic material from inorganic sources provided by the environment (e.g. photosynthesis). Heterotrophs are organisms which derive their energy from consuming other organisms (consumers, herbivores, carnivores).

Question 11

Based on their mode of nutrition, organisms can be divided into what three groups? Give definitions.

Answer 11

Producers: produce their own energy, e.g. photosynthesis or chemosynthesis.

Consumers: feed on living organisms by ingestion.

Decomposers: break down organic matter and play important role in food webs and nutrient cycling.

Question 12

What are the two types of decomposers?

Answer 12

Detritivores: obtain nutrients from detritus (decomposing plant and animal matter) by internal digestion - normal digestion(e.g. earthworms and starfish).

Saprotrophs: obtain nutrients from dead organisms by external digestion - grow on or around their food source (e.g. fungi and soil bacteria)

Question 13

What is nutrient cycling, why is it important, and who does it?

Answer 13

Nutrient cycling is the use, movement, and recycling of nutrients in the environment because valuable elements like carbon, oxygen, hydrogen, phosphorus, and nitrogen are essential to life and must be recycled in order for organisms to exist. Also, nutrient cycling allows ecosystems to remain sustainable for long periods of time. Producers, consumers, and decomposers allow nutrients to be cycled through an ecosystem.

Question 14

Describe the 5 steps of nutrient cycling.

Answer 14

1. Nutrients taken up by producers as simple inorganic molecules.
2. producers incorporate the nutrient into complex organic molecules
3. the producer is eaten and nutrients pass to the consumers
4. the nutrients are then passed along a food chain
5. when both the producer and consumer die saprobiotic microorganisms break down the molecules releasing the nutrients and the cycle begins again.

Question 15

What is species distribution? And what are limiting factors?

Answer 15

Species distribution is the range of places that a species inhabits. This is influenced by limiting factors: factors which limit the population growth and size. They can be density dependent (related to population size, e.g. food availability, competition, predation, habitat, etc.) or density independent (not related to population size, e.g. weather and climate)

Question 16

What is an ecological niche?

Answer 16

The role that a species fills within an ecosystem and the match of a species to a specific environmental condition. This includes spatial habitat (where it lives), mode of nutrition, and interactions with other species, as well as the position or job of a species within its ecosystem.

Question 17

What is a keystone species?

Answer 17

Keystone species will have a disproportionately large effect of the communities in which they occur, they control populations of other species that would otherwise negatively dominate, or they provide critical resources for a wide range of species. E.g. otters, wolves, bees.

Question 18

What is symbiosis? What are the two types?

Answer 18

Symbiosis refers to organism interactions where two different organisms live together in close contact. There is obligatory symbiosis: where it is essential for life and there is facultative symbiosis: where it is beneficial for at least one organism, but not essential.

Question 19

What are the 6 kinds of symbiosis?

Answer 19

Commensalism: one species benefits while the other is neither harmed nor benefitted.

Mutualism: both benefit

Parasitism: one is harmed, one benefits.

Predation: one species kills and consumes the other

Herbivory: consumers feed on producers

Competition: use of the same limited resource by 2 species in the same area.

Question 20

What are trophic levels?

Answer 20

Where an organism is situated on a food chain. Organisms can occupy more than one trophic level due to the web-like nature of many feeding relationships and they can also be part of more than one food chain. Producers always occupy the first trophic level, primary consumers feed on producers and hence occur the second level, further consumers (secondary, tertiary, etc.) will occupy the next levels.

Question 21

What do food chains show?

Answer 21

Food chains show the linear feeding relationships between species in a community. They used arrows to show the flow of energy in the community as one organism is eaten by another (arrows point to where the energy is flowing to).

Question 22

What is the energy transfer 10% rule?

Answer 22

Only approximately 10% of energy is transmitted to the next trophic level. The other 90% is lost as heat in cellular respiration, energy for movement, reproduction, etc. materials not eaten by consumer, and undigested food matter which is excreted. This can be demonstrated with an energy pyramid. Generally, ecosystems cannot support more than 4 trophic levels because there is not enough energy (you just run out of energy because of the 10% rule).

Question 23

Describe food webs.

Answer 23

Many food chains joined together, they are used to show relationships between trophic levels and populations within a community. They can include dead animals and decomposers which are necessary to recycle nutrients from living things back into the soil.

Question 24

What is biomass?

Answer 24

the dry mass of living biological organisms in a given area or ecosystem at a given time (it is the amount of energy available on the trophic level/for an organism to eat).

Question 25

What is gross production?

Answer 25

The total amount of organic matter produced by a trophic level in an ecosystem (some of that energy is lost during respiration so the net production is the amount left after respiration). Net production can be found using the equation: net production = gross production - respiration. For producers this can also be represented as: glucose available for consumers = glucose made - glucose used.

Question 26

What are the main three factors which determine an ecosystem’s productivity?

Answer 26

temperature, precipitation, and insolation (sunlight) If an ecosystem is warmer and has lots of rain like a rainforest, it will be more productive than a place that is hot with good sunlight but no rain, like a desert.

Question 27

What is a climograph?

Answer 27

A graph which shows the average precipitation and temperature for an area. It is used to compare climates of different areas.

Question 28

What are optimum range, zone of stress, and zone of intolerance?

Answer 28

Often used in a bell curve, optimum range shows the preferred environment factors of an organism, zone of stress shows where the factors would be dangerous for the organism but they could still survive, and zone of intolerance shows where the factors would be deadly for the organism.