Ecosystems - 3B

Question 1

Carry capacity

Answer 1

maximum number of living things (like fish, animals, plants) that an environment can handle without running out of stuff they need to survive—like food, space, clean water, or shelter.

Question 2

What happens when a population reaches carrying capacity?

Answer 2

When a population approaches its carrying capacity, the rate of increase slows, and the birth rate equals the death rate. Leading to 0 population growth).

Question 3

Population size

Answer 3

The number of individuals of a species living in a defined area.

Question 4

How Resources Affect Population Size

Answer 4

Population size depends on resources. If resources go up, more animals survive. If resources go down, carrying capacity drops. Too many animals can damage the environment, leading to a cycle.

Question 5

What are two main strategies ecologists use to estimate population size, and when are they used?

Answer 5

1. Direct Counting
   How it works: Count individuals in a small, defined area
   Examples:
   Point count (counting animals passing a fixed point)
   Counting nests or burrows
   Best for:
   Easily visible species
   Low movement during counting
   e.g. dragonflies, turtles, lions, whales
2. Sampling
   How it works: Count part of the population and estimate the total
   Examples:
   Quadrats (small sample frames)
   Mark-recapture (tagging and tracking individuals)
   Best for:
   Large areas or populations
   Quadrats: low movement (e.g. snails)
   Mark-recapture: high movement (e.g. birds, fish, mice)

Question 6

modelling population size?

Answer 6

Modelling means creating a visual or mathematical representation of how a population changes over time. It helps scientist understand patterns, predict future changes and spotting sudden changes.

Question 7

seasonal changes

Answer 7

The weather (aka abiotic factors) changes
That means resources like food and water change too. So, animal populations go up or down depending on what’s available. seasonal changes affect population size in predictable ways. Things like breeding, dormancy, migration, and death rates shift with the seasons, causing regular ups and downs in how many animals are in an area.

Question 8

Human - driven habitat destruction

Answer 8

Not all changes are regular, however, habitat destruction due to human activity dramatically reduces carrying capacity and can have long term, negative impacts. E.g pollution, coral bleaching, deforestation.