Ecology Quiz: Ecosystems and Interactions

Study Notes

Hong Kong has many different natural environments
Organisms in an ecosystem interact with one another and with their environment, creating stable, self-supporting systems
Different types of ecosystems exist in Hong Kong, including freshwater streams, mangroves, woodlands, grasslands, and rocky shores
Key characteristics vary between ecosystems (e.g. water availability, temperature, soil type.)

Ecology is the study of interrelationships between organisms and their environment
Levels of organization include species, populations, communities, ecosystems, biomes, and biosphere
Organisms within a habitat have specific interactions to maintain a self-supporting/stable/dynamic ecosystem

Abiotic factors are non-living components of an ecosystem
Examples include temperature, light, rainfall, humidity, wind speed, water current, salinity, oxygen level, and substratum characteristics
These factors greatly affect organism distribution in ecosystems, and organisms have adaptations in response to these factors

Biotic factors are the living components of an ecosystem
Populations of organisms may compete, interact in mutualistic, commensalistic, and parasitic relationships, or engage in predation.
The species richness and abundance in a community determine its species diversity; the influence of a dominant species on diversity
Common terms refer to niche and habitat. Habitat is an organism's address, and a niche is an organism's role in a community. Niche attributes are (1) temperature range the organism resides in, (2) types of food the organism eats and (3) the space it occupies. A population of two species cannot coexist if their niches are the same.

Energy flow is not a cyclic process, instead is lost as heat through many processes
Organisms in different trophic levels (producer, primary, secondary, tertiary) transfer chemical energy
Energy flow through a food chain
Energy lost in different activities (respiration, uneaten materials, excretion, undigested matter).
Role of decomposers: Break down organic matter and release nutrients into the soil, which is necessary for producers to grow.

Ecological succession is the gradual change in the plant and animal communities in a habitat over time/process of ecological change
Primary succession occurs in areas where no soil exists (e.g. after a glacier retreats or volcanic eruption)
Pioneer species colonize barren areas, gradually forming soil, and eventually forming a climax community of plants.
Secondary succession takes place in areas that once had soil and organisms (e.g. after a fire)
The pioneer species are often grasses, shrubs, and small trees that are capable of colonizing the area rapidly
A climax community eventually is formed.

Pyramids of numbers and biomass summarize energy transfer within a food chain
Pyramids generally narrow as trophic levels increase, reflecting the loss of energy between levels
Pyramid of numbers reflects number of organisms at each trophic level
Pyramid of biomass shows total dry mass of organisms at each level
Pyramids may also be inverted (e.g. a single tree supports many insects) due to differences in organism size, lifespan, and reproductive rate.

Human activities have significantly impacted ecosystems
Overexploitation, pollution, habitat destruction, and global warming cause harm
Loss of biodiversity (variety of species) is one key result
Conservation efforts are essential (e.g., waste reduction, habitat protection, alternative energy).

Quadrat sampling: Used to estimate the abundance (density and percentage cover) of non-mobile/slow-moving organisms.
Line transect sampling: Used to study the distribution of immobile organisms. It involves measuring the presence or absence of species along a line.
Belt transect sampling: Involves sampling along a line using quadrats at regular intervals or continuously along the line, providing more accurate estimation of the abundance of organisms and identifying the transition between different communities

The carbon cycle involves the movement of carbon between the atmosphere, organisms, and the soil. Key processes include respiration, photosynthesis, combustion, and decomposition.
The nitrogen cycle describes the movement of nitrogen, including nitrogen fixation (converting atmospheric nitrogen into usable forms for plants) and nitrification (converting ammonia to nitrates).