Ecosystems and Biomes
Why do equatorial ecosystems typically have higher net primary productivity than ecosystems at high latitudes?
Warm, moist conditions allow year-round photosynthesis, long growing seasons, and rapid plant growth.
How do crude birth rate and crude death rate determine population growth?
Growth rate ≈ (CBR − CDR)/10
Why is total biomass in the open ocean high despite low productivity per unit area?
The ocean covers most of Earth, so low productivity across a massive area yields high total biomass.
Compare r-selected and K-selected species.
r-selected: many offspring, low care.
K-selected: few offspring, high care.
What are the 3 different types of plate boundaries? describe them
divergent <-->
convergent-><-
transform II
Many tropical rainforest soils are highly weathered and nutrient-poor, yet the biome has enormous biodiversity. Explain this paradox in terms of nutrient cycling and soil characteristics.
Heavy rainfall leads to nutrient leaching and low soil nutrient storage, but extremely fast decomposition and rapid nutrient uptake by vegetation keep nutrients cycling within biomass rather than soil.
Describe two demographic shifts that occur as a country industrializes.
Birth rates fall; death rates fall; urbanization increases; access to education and healthcare improves.
Why do upwelling zones support major fisheries?
Nutrient-rich deep water rises, boosting phytoplankton growth and supporting large food webs.
How can varying food resources cause evolutionary divergence within the same species?
Different food types create selective pressure, favoring different traits in different locations.
Describe the rain-shadow effect using the terms adiabatic heating and cooling, and latent heat release
As air is forced up over a mountain, it cools, which is adiabatic cooling, at this point, the saturation point drops and precipitation is released. The air is now cool and dry. Then, as it goes down the other side of the mountain, it heats up which is adiabatic heating. The air is now hot and dry.
Why is nitrogen often a limiting nutrient in ecosystems even though the atmosphere is 78% nitrogen gas?
Most organisms cannot use atmospheric N₂; nitrogen must be converted into usable forms like ammonia or nitrate through nitrogen fixation.
How is population doubling time calculated using the Rule of 70, and what assumption is required?
70 ÷ growth rate; assumes constant exponential growth.
What does HIPPO stand for?
H- habitat loss
I- invasive species
P- Pollution
P- Population Growth
O- Overharvesting
What are species richness and evenness?
richness is the number of different species in an area and evenness in their population sizes relative to each other.
How can rising ocean temperatures disrupt upwelling, and what happens as a result?
Weakening temperature gradients suppress upwelling, reducing nutrient availability and lowering fish populations.
Why do late-successional tree species have difficulty recolonizing immediately after a disturbance like clear-cutting?
They grow slowly, need shade-tolerant conditions, and are outcompeted by fast-growing pioneer species.
What is population momentum and what age-structure pattern causes it?
Continuing population growth despite falling fertility due to a large number of young people entering reproductive age.
Why do isolated islands have both high extinction rates and unique species adaptations?
Small populations and low resources increase extinction risk; isolation limits gene flow, enabling unique traits to evolve.
What are the 3 different types of biodiversity
genetic, species, ecosystem
what is the difference between weathering and errosion?
Two biomes receive equally low precipitation, yet one has far more reptile species. Why?
Temperature limits reptile metabolism—cold biomes reduce ectotherm activity, while warm deserts support diverse reptile life.
A country with below-replacement fertility is still growing. Why?
Large youth population and increased life expectancy keep population increasing despite low fertility.
How do grazing animals such as cattle or bison assist in nutrient cycling?
returning nutrients via urine and feces, stimulating plant growth, breaking down plant litter, improving soil structure with their hooves, and increasing microbial activity
You are in a forest, please give me one provisioning service and one regulating service
provisioning: lumber, water, something that is directly taken from the ecosystem
regulating: removal of CO2, flood control from roots, creation of oxygen, something that maintains environmental conditions
During an El Niño event, what happens to the trade winds along the equatorial Pacific?
They weaken or reverse direction, reducing the upwelling normally found along the western coast of South America.