LEVELS OF BIODIVERSITY
Name the four levels of biodiversity
Genetic, species, habitat, and ecosystem diversity
Name the four categories of ecosystem services.
Provisioning, regulating, cultural, and supporting.
If there are 2 islands, which would have the highest species richness, and why?
Island A, because the theory of island biogeography states colonization rate is inversely related to distance from the mainland
Classify each as periodic, episodic, or random: (a) ocean tides, (b) wet and dry cycles every 5–10 years, (c) a volcanic eruption.
(a) Periodic, (b) episodic, (c) random.
Which type of succession begins on bare rock with no soil, and which begins after a disturbance when soil is still present?
Primary succession begins on bare rock. Secondary succession begins where soil remains.
A pond contains 40 frogs, 25 snails, 10 dragonflies, and 5 minnows. What is its species richness, and what does that term measure?
Species richness is 4. It is the number of different species in an ecosystem, regardless of how many individuals each has.
Classify each by service category: (a) timber harvested from a forest, (b) a wetland filtering pollutants from water, (c) bees pollinating crops, (d) scenic hiking in Grand Teton National Park.
(a) Provisioning, (b) regulating, (c) supporting, (d) cultural.
Define ecological tolerance, and explain how it can apply to both an individual and a species.
It is the range of conditions (temperature, salinity, flow rate, sunlight, etc.) an organism can endure before injury or death. It can be described for a single individual or for a whole species, where the species range reflects the tolerances of its members.
True or false, and explain: “A giraffe stretched its neck to reach high leaves, so its offspring were born with longer necks.”
False. Traits acquired during an individual’s life are not passed on. Heritable variation already existed, longer-necked individuals survived and reproduced more, and the population changed over generations.
What is a pioneer species? Give an example.
One of the first species to colonize disturbed or barren habitat, able to survive with little or no soil. Examples are lichens and mosses.
Explain how a population bottleneck affects genetic diversity, and why that makes the population more vulnerable to environmental stressors.
A bottleneck sharply reduces population size, so the survivors carry only a fraction of the original genetic variation. With less variation, fewer individuals may have traits that help them survive a new stressor such as disease or climate change (cheetahs are the classic example).
What does the “replacement value” of an ecosystem service mean, and why is it useful for decision-making?
It is the cost of replacing a natural service with human technology, such as building a water-treatment plant to replace wetland filtration. It puts a dollar figure on services that are otherwise treated as free, so protecting an ecosystem can be compared with the cost of losing it.
Trout survive in a narrow temperature range, while carp survive across a wide range. If a stream warms by 5°C, which species is more likely to stay, and which is the specialist?
Carp are more likely to stay. Trout are the specialist, with a narrow tolerance. Warming past the trout’s tolerance limit causes injury or death.
A field is sprayed with a pesticide and most insects die. A few survive, and later generations are mostly resistant. Explain this using natural selection.
Genetic variation (from mutation and recombination) meant some insects already had a resistance allele. Resistant individuals survived, reproduced, and passed on the allele, so its frequency in the population increased over generations.
A beaver dam transforms a stream into a wetland. The presence of mayfly larvae signals clean water. Which species is a keystone species, which is an indicator species, and what is the key difference?
The beaver is the keystone species and the mayfly is the indicator species. A keystone species has a disproportionately large effect on community structure. An indicator species reveals a condition of the ecosystem through its presence, abundance, or scarcity, without necessarily shaping the community.
A large forest is cleared and fragmented. Which group of species is lost first, which group follows, and what kind of species also declines because of the space it needs?
Specialists are lost first, then generalists. Species with large territorial requirements (e.g., large predators like panthers or wolves) also decline.
Name two causes of pollinator decline, and explain one economic and one ecological consequence of losing pollinators.
Causes include pesticides, habitat loss, disease/parasites, and climate change (any two). Economic: lower crop yields and higher food costs. Ecological: reduced plant reproduction, which affects the food webs and species that depend on those plants.
How does a realized niche differ from a fundamental niche, and what usually explains the difference?
The fundamental niche is the full range of conditions a species could survive, grow, and reproduce in. The realized niche is where it actually lives, which is usually narrower because of biotic interactions such as competition and predation.
Ice cores show that atmospheric CO₂ and temperature rose and fell together over the last 400,000 years. Describe the relationship, and explain why this data alone doesn’t tell us the cause of every past climate change.
CO₂ and temperature have a strong positive relationship: when one is high, the other is high. Correlation alone doesn’t show cause. Earth’s climate has changed for many reasons (orbital changes, volcanic activity, solar output, feedbacks), and CO₂ can be both a driver and a response.
Describe how total biomass, species richness, and net productivity change as an abandoned farm field undergoes secondary succession.
Biomass increases over time and levels off at maturity. Species richness increases early and then levels off or peaks mid-succession. Net productivity is highest in early to mid succession and levels off or declines in a mature community.
Community 1 has 25 individuals each of 4 species (100 total). Community 2 has 91 individuals of Species A and 3 individuals each of three other species (100 total). Compare their richness and evenness, say which is more diverse, and explain why that matters for recovery from a disruption.
Both have a richness of 4. Community 1 has much higher evenness, so it is more diverse. Ecosystems with more species, evenly represented, are more likely to recover from disruptions because losing one species changes the community less and more species can fill its roles.
A coastal wetland is drained for development. Identify two ecosystem services lost, each from a different category, and describe one economic and one ecological consequence.
Any two from different categories, for example regulating (flood and storm buffering, water filtration, carbon storage) and provisioning (fish and shellfish) or cultural (recreation). Economic: higher storm damage and water-treatment costs, or lost fishing income. Ecological: loss of habitat and biodiversity, and reduced water quality.
Why do many island species evolve to be specialists, and how does that make them vulnerable to invasive species?
Islands have limited food and territory, which favors species adapted to a narrow niche. Invasive species are typically generalists that can outcompete specialists, and island natives often lack defenses against them
A lake warms rapidly over ten years. Describe the three possible fates for a cold-water fish population, and explain which is most likely if the population has very low genetic diversity.
Individuals may alter their behavior (e.g., use deeper, cooler water), move to a new area, or perish (local extinction). With low genetic diversity there is little variation for selection to act on, so adaptation is unlikely and the population is most likely to perish. Adaptation also requires incremental genetic change over generations, which is too slow for a rapid shift.
In a rocky intertidal experiment, researchers removed the sea star Pisaster from one plot. Over two years, mussels took over the plot and species richness fell from 15 to 8, while an untouched control plot stayed at 15. Is the sea star a keystone species or an indicator species? Support your answer with a claim, evidence, and reasoning.
Claim: keystone species. Evidence: removing it dropped richness from 15 to 8, while the control plot stayed at 15. Reasoning: the sea star preys on mussels and keeps them from dominating, which frees space for other species, so its activity determines community structure. An indicator species would only signal conditions, not cause the change.