Births, Deaths & Balance
A population has 10 births and 10 deaths in one year. What happens to the population size? Explain why.
The population remains stable because there is an equal number of births and deaths.
Why can’t organisms reproduce if they don’t have enough energy?
This is simply because reproduction requires energy.
What happens to a consumer population if its food source disappears?
The population will also begin to decrease over time.
Two populations eat the same food. What happens if that food becomes scarce?
The populations will begin to decrease as there is not enough energy storage molecules for survival and reproduction.
Why can a population be affected by another population it doesn’t directly eat?
Two populations can compete for the same resource population. A change to one of these populations affects the size of the other.
A population has more deaths than births for several years. What trend will you see over time?
The population will decrease over time.
A population has plenty of food. What should happen to reproduction? Why?
Reproduction should increase as there is more food availability (more resources).
Why does a growing consumer population cause more deaths in a resource population?
The consumer populations needs more to eat to survive and reproduce.
Why might one population grow while another shrinks even though they use the same resource?
The two populations are in competition. So the one that has a greater population needs more energy storage molecules causing the other population to shrink.
A plant population decreases. Name two populations that could be affected and explain how.
Herbivores and their consumer population or competing herbivore populations.
Two populations start the same size. One stays stable, the other shrinks. What might be different about their birth and death rates?
The first population has equal births and deaths. The other population has fewer births than deaths.
Two populations eat the same food, but one reproduces more. What might explain the difference?
One population could be larger than the other.
A resource population increases. Predict what will happen next to the consumer population.
The consumer population should also increase since there are more energy storage molecules available.
How does competition affect energy available to each population?
If consumer populations are in competition for the same resource population, they are competing for the same energy storage molecules.
How does a food web help scientists predict population changes?
A food web allows scientists to see how energy is transfer throughout populations. With these transfers, scientists can see which populations might be affected by a change in another.
A population stays the same size even though organisms are being born and dying. How is that possible?
It is possible because there is an equal number of births and deaths.
A population gets less food but survives. Why might reproduction decrease before the population dies out?
Reproduction would decrease because there is not enough energy storage molecules.
A consumer population grows too large and then crashes. What likely caused this pattern?
The population originally had a lot of energy storage molecules available but then the demand for resources could not keep up as they needed more energy to survive and reproduce. So they crashed.
One competing population is removed. What happens to the other population, and why?
The other population increases because the resource population no longer has two competing consumer population. This leaves more energy storage molecules for the remaining consumer population.
Explain how a change in one population can cause a chain reaction across an ecosystem.
A change changes the flow of energy (ESMs) which can then affect survival and reproduction in connected populations.
A population suddenly begins growing quickly. What are two different reasons this could be happening?
There is an increase in the resource population or a decrease in the consumer population.
How does energy availability limit how large a population can get?
A population can only get as large as the amount of resources available.
How can changes in one population lead to instability in another connected population?
The size of a population can be affected by any population that is connected to it in a food web, even if they are not directly connected.
How can competition between two populations cause indirect effects on a third population?
Two populations can compete for the same resource population. A change to one of these populations affects the size of the other. This can lead to changes in size for indirectly related populations.
A consumer population increases quickly, but its resource population does not. Predict what will happen next and explain your reasoning.
Increased eating of the resource population
Decrease in resource population
Less energy available
Later decrease in consumer population
Possible indirect effects on other populations