Ecosystem Changes
What does resource availability mean?
The amount of food, water, shelter, and other resources available to organisms in an ecosystem.
What is salinity?
The amount of salt in water.
What is deforestation?
Removing or clearing forests.
Are climates near the equator moist and hot or dry and hot?
moist and hot
Scientists study a grassland where rabbits eat grass.
Year 1: Rainfall = 60 cm; rabbit population = 120
Year 2: Rainfall = 40 cm; rabbit population = 85
Year 3: Rainfall = 20 cm; rabbit population = 50
How many rabbits were recorded in Year 3?
50 rabbits.
A disease kills many rabbits. What may happen to foxes that eat rabbits?
Foxes may decrease because they have less food/ disease will be spread to foxes.
Which usually has higher salinity: a freshwater lake or the ocean?
The ocean.
A forest is cleared to build houses. What happens to the available habitat for forest animals?
It decreases.
Which biome is warm year-round, receives heavy rainfall, and has many trees?
Tropical rainforest.
Scientists study a grassland where rabbits eat grass.
Year 1: Rainfall = 60 cm; rabbit population = 120
Year 2: Rainfall = 40 cm; rabbit population = 85
Year 3: Rainfall = 20 cm; rabbit population = 50
As rainfall decreased, what happened to the rabbit population?
It also decreased.
A drought causes less grass to grow. How could this affect rabbits?
Rabbits may decrease because less food is available.
Freshwater from a river mixes with ocean water. What aquatic ecosystem forms there?
An estuary.
People catch fish faster than the fish can reproduce. What is this called, and what may happen to the fish population?
Overfishing; the fish population may decrease.
A biome has little precipitation and few plants. What other information would help you decide whether it is a desert or tundra?
Its temperature. Tundra is very cold year-round, with short, cool summers. A hot climate would point toward a desert.
Scientists study a grassland where rabbits eat grass.
Year 1: Rainfall = 60 cm; rabbit population = 120
Year 2: Rainfall = 40 cm; rabbit population = 85
Year 3: Rainfall = 20 cm; rabbit population = 50
Which question can these data answer?
A. How did rainfall and rabbit numbers change over the three years?
B. Which disease infected the rabbits?
A. The data show rainfall and rabbit numbers, not disease information.
Frogs decrease during a year with little rainfall. Does this prove disease caused the decrease? Explain.
No. Less rainfall could reduce water or food. We need evidence that frogs were sick.
A fish lives where salinity changes throughout the day. How would tolerating different salt levels help it survive?
It could survive changes in the water’s salinity.
A new species eats the same food as native fish. It reproduces quickly and harms the native fish population. Explain how it could cause native fish to decrease.
It competes with native fish for food, leaving fewer resources for them.
How are a desert and tundra alike? How is a hot desert different from tundra?
Both receive very little precipitation and have few plants. A hot desert has hot days, while tundra has very cold temperatures and short, cool summers.
Scientists study a grassland where rabbits eat grass.
Year 1: Rainfall = 60 cm; rabbit population = 120
Year 2: Rainfall = 40 cm; rabbit population = 85
Year 3: Rainfall = 20 cm; rabbit population = 50
A student says, “Rabbit numbers decreased as rainfall decreased.” Use numbers to support this statement.
Rainfall dropped from 60 cm to 20 cm, while rabbit numbers dropped from 120 to 50.
A rabbit population decreases. One student blames limited food; another blames disease. What evidence would help decide?
Check whether food decreased and whether rabbits showed signs of illness when the population declined.
Both a cactus and an estuary fish have adaptations. Explain how storing water helps the cactus and tolerating changing salinity helps the fish.
Water storage helps the cactus survive dry conditions. Salinity tolerance helps the fish survive where fresh and salt water mix. Both adaptations fit their environments.
After an oil spill, a whale population decreases. Which TWO observations would support the explanation that the spill contributed to the decrease?
A. The whales’ prey decreased.
B. An unexposed whale group stayed stable.
C. Bird nests increased far inland.
A and B. Less prey means less food, and the stable unexposed group helps support a connection to the spill.
An ecosystem has strong winds, very cold temperatures, and few trees. Which question would best help confirm that it is tundra?
A. Are there predators?
B. Does it have permanently frozen ground?
C. Do birds live there? Explain.
B. Permanently frozen ground helps identify tundra. Predators and birds occur in many biomes.
Scientists study a grassland where rabbits eat grass.
Year 1: Rainfall = 60 cm; rabbit population = 120
Year 2: Rainfall = 40 cm; rabbit population = 85
Year 3: Rainfall = 20 cm; rabbit population = 50
A student says, “Less rain caused less grass, which caused fewer rabbits.” What part of the explanation was NOT measured? What should scientists collect next?
Grass availability was not measured. Scientists should measure grass growth or coverage to test that part of the explanation.