Bio1B Ecology Midterm Study Guide

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Consider the Andes mountain range in South America, which extends from near the equator to latitudes above 50°S. Along this range, there is significant variation in both temperature and precipitation. The eastern slopes of the Andes receive high levels of precipitation, while the western slopes, particularly in the Atacama Desert region, are among the driest places on Earth.

Which of the following best explains the variation in temperature and precipitation along the Andes, both latitudinally and elevationally?

 

As latitude increases, the Andes experience cooler temperatures due to lower solar radiation, while the eastern slopes receive more precipitation because the rising air from the Amazon basin cools and condenses. On the western side, descending air warms and dries, creating arid conditions.

Imagine a mountain range with an environmental gradient from low to high elevation. This range consists of three distinct habitats: lowland forest, montane forest, and alpine meadow. The following mammal species are observed in each habitat:

• Lowland Forest: White-tailed Deer, Eastern Cottontail, Black Bear, Red Fox, Bobcat

• Montane Forest: Black Bear, Red Fox, Mountain Lion, Snowshoe Hare

• Alpine Meadow: Mountain Lion, Snowshoe Hare, Pika, Marmot, Bighorn Sheep, Wolverine

What is the alpha diversity for each habitat? Hint: this is also known as the species richness. 

 

Lowland Forest: 5, Montane Forest: 4, Alpine Meadow: 6

Imagine a mountain range with an environmental gradient from low to high elevation. This range consists of three distinct habitats: lowland forest, montane forest, and alpine meadow. The following mammal species are observed in each habitat:

• Lowland Forest: White-tailed Deer, Eastern Cottontail, Black Bear, Red Fox, Bobcat

• Montane Forest: Black Bear, Red Fox, Mountain Lion, Snowshoe Hare

• Alpine Meadow: Mountain Lion, Snowshoe Hare, Pika, Marmot, Bighorn Sheep, Wolverine

Using the information above on species composition in each habitat, calculate the beta diversity between the following pairs of habitats:

I. Lowland Forest and Montane Forest

II. Montane Forest and Alpine Meadow

III. Lowland Forest and Alpine Meadow

I. Beta: 5, II. Beta: 6, III. Beta: 11

What abiotic factors are most likely to set species range limits in terrestrial and aquatic environments? Choose the single best answer

 

Temperature and precipitation in terrestrial environments, light and nutrients in aquatic environments

Which of the following describes a relationship between two species when one benefits while the other is harmed? Choose the single best answer. 

Parasitism

The principle of competitive exclusion states: Choose the single best answer. 

 

Two species that have exactly the same niche cannot coexist in a community

Both bald eagles and ospreys, and wading birds and large piscivorous fish

40 years ago, bald eagles were in danger of extinction throughout most of their range in the United States, due to habitat destruction, illegal hunting, and pollution. If bald eagles exert strong top-down control over this food web, how would their decline have affected phytoplankton, and benthic invertebrates? Choose the single best answer.

 

Phytoplankton increase, benthic invertebrates decrease

Classify the following cases as direct, zoonotic, or vector transmission:

i) Chestnut blight spores are blown through the wind to a neighboring tree

ii) A mosquito bites a bat infected with dengue virus and then a human, transmitting the virus to the human

iii) Race horse trainers in Australia became ill with Hendra virus, after working with infected racehorses. The virus originated from bats.

iv) SARS-CoV-2 (the virus causing COVID-19) is transmitted from person to person through aerosol droplets

Direct, vector, zoonotic, direct

Which of the following best explains why there is typically less biomass and fewer individuals at the top of a food chain than at the bottom? Choose the single best answer.

 

Energy is lost at each trophic level, limiting the energy available to support higher-level consumers.

Why might nutrient influx from fertilizer runoff initially increase primary production in aquatic ecosystems? Choose the single best answer.

 

Nutrients promote the growth of photosynthetic organisms, which increases primary production.

A landslide removes vegetation and topsoil from a mountain slope, exposing bare rock. Which type of succession will likely occur first, and what are the initial species expected to colonize this area? Choose the single best answer.

 

Primary succession; lichens and mosses

How might evolutionary processes, such as natural selection, differ between the early and late stages of primary succession? Choose the single best answer.

 

Early stages favor species with traits for rapid colonization and resilience to harsh conditions, while late stages favor species with traits for competition and resource specialization.

A country is in stage 2 of the demographic transition, with rapidly declining death rates but still high birth rates. Which of the following consequences is most likely?

A population boom that strains public health and infrastructure.

Agricultural fertilizer use has greatly increased nitrogen availability. Which long-term effect most directly illustrates a disruption of the nitrogen cycle?

 

Dead zones in coastal ecosystems.

Fragmentation reduces habitat connectivity. Which consequence is most likely for a large carnivore?

 

Higher extinction risk due to small population size in patches.

Which of the following is a positive climate feedback loop involving the carbon cycle?

 Warming reduces snow and ice cover, which decreases Earth’s reflectivity (albedo) and causes further warming.

Which scenario best illustrates a trophic mismatch caused by phenological change?

 

Trees leafing out earlier, supporting early herbivores while birds lag behind.

A government prioritizes conserving a charismatic species (e.g., pandas) over lesser-known species. Which ethical concern does this raise?

 

Intrinsic value of all species versus instrumental value.

Which of the following is the correct order from smallest to largest in the biological hierarchy?

Population, Species, Community, Ecosystem

A population is best described as:

All individuals of a single species living in a specific geographic area

If a researcher is studying the effect of pollution on a lake and the organisms that live within it, which level of biological organization is primarily being studied?

Ecosystem

A community differs from a population in which of the following ways?

A community consists of all the different populations of species living in the same area, while a population consists of individuals of one species.

Which of the following is an example of a biotic factor in an ecosystem?

Predators

Abiotic factors in an ecosystem include all of the following except:

Competition

Which of the following are primary abiotic factors influencing the ecology of terrestrial biomes?

Temperature and precipitation

The field of Ecology primarily studies:

Interactions between organisms and their environment

Which of the following best describes Traditional Ecological Knowledge (TEK)?

Knowledge passed down through generations by indigenous peoples, concerning their local ecosystems

community

group of different species living in a connected area

A study finds that species living in fragmented patches experience higher rates of local extinction than those in continuous habitats. Which of the following ecological processes is most likely contributing to this pattern?

Smaller population sizes in patches making species more vulnerable to stochastic events

Type I Survivorship Curve

High survival rates early and middle in life, with most individuals living to old age. Mortality is concentrated in older age groups.

Type 3 Survivorship Curve

High mortality in early life, but survivors have high chances of living to adulthood. Associated with many offspring, with little to no parental care.

Explain the concept of life history trade-offs. How do these trade-offs influence the variation observed in life history strategies?

Life history trade-offs involve balancing the costs of reproduction with somatic maintenance. This leads to the life history strategies such as semelparity and iteroparity.

population

group of the same species living in one connected area

ecosystem

all the organisms living in an area, plus the abiotic environment

Which of the following is an example of a pathogen?

Bacterium

What is a species’ fundamental niche?

The range of environmental conditions a species can potentially occupy.

Which of the following best describes a species' realized niche?

The part of its fundamental niche that a species actually occupies in the presence of biotic interactions such as competition

Which of the following is an example of a density-dependent regulator of population growth?

Predation

Semelparity

is a reproductive strategy where an organism reproduces only once in its lifetime, often producing a large number of offspring.

Iteroparity

A reproductive strategy in which organisms reproduce multiple times over the course of their lifetime, typically producing fewer offspring per event but investing more in parental care and survival between reproductive cycles.

Vector-borne Diseases/Transmission

Pathogen transmitted to humans from reservoir through a vector species (often, arthropods – mosquitoes, ticks etc)

Zoonotic

Pathogen resides in a second species, transmitted directly to humans from that species

Direct transmission

The immediate transfer of a pathogen from an infected individual to a susceptible host through direct contact

BIDE

Birth, Immigration, Death, Emigration

Stage 1

High mortality and birth rates. Both birth and death rates are high, keeping population growth slow and stable; common in pre-industrial societies.

Stage 2

Mortality falls but birth rates stay high. Death rates fall due to better health, sanitation, and food, but birth rates remain high, causing rapid population growth.

Stage 3

Mortality stays low and births fall. Birth rates begin to decline as education, urbanization, and access to contraception improve, slowing population growth.

Stage 4

Mortality and birth rates low. Both birth and death rates are low, leading to a stable or slow-growing population typical of developed nations.

Stage 5

Birth rates fall below death rates, causing population decline and aging, seen in some highly developed countries.

Density Independent Factor

Factor that affects population size regardless of its density, usually involving abiotic events like weather, natural disasters, climate, or human disturbances (e.g., floods, wildfires, droughts).

Density Dependent Factor

factor affects population size more strongly as population density increases, often involving biotic interactions like competition, predation, disease, or parasitism.

Type 2 Survivorship Curve

Constant mortality rate throughout life; the chance of dying is roughly equal at any age.Typical of species with moderate parental care

R selection

selects for life history traits that maximize reproduction and the ability for a population to increase rapidly at low density

K selection

selects for life history traits that enhance an individual’s fitness when a population is fairly high (close to carrying capacity) and stable.

Intra-specific competition

the struggle for limited resources between members of the same species.

inter-specific competition

individuals of different species compete for the same limited resources, such as food, water, or territory

Tropical Forest

Temperature: hot and wet year round
Precipitation: very rainy

Biodiversity: high, due to consistent environment

Kinds of Organisms / Adaptations: camouflauge

Chaparral

Temperature: hot and dry summers, cold and mild winters
Precipitation: rainy in the winter, dry in the summer

Biodiversity: moderate

Kinds of Organisms / Adaptations: fire resilience and drought resilience

Tundra

Temperature: cold all year
Precipitation: little to none

Biodiversity: low

Kinds of Organisms / Adaptations: resilient to cold temperatures, ability to migrate

Coniferous Forest

Temperature: cold winters, moderate summers
Precipitation: moderate

Biodiversity: moderate

Kinds of Organisms / Adaptations: evergreen, waxy needles for water preservation, cone shaped for snow

Desert

Temperature: hot
Precipitation: low

Biodiversity: low / moderate

Kinds of Organisms / Adaptations: water saving, resilient to extreme temperatures,