ecology midterm 2

What is the primary concern about trophy hunting in bighorn sheep populations?

It removes the largest and strongest males, potentially hindering population recovery.

How has commercial fishing for cod influenced the size and age at sexual maturity?

It has caused cod to mature at younger ages and smaller sizes.

How does natural selection contribute to the accumulation of differences between populations?

By favoring individuals with different traits in different environmental conditions, leading to genetic divergence.

What is meant by "ecological trade-offs" in the context of adaptation?

Energy and resources spent on one function may limit the ability to perform another.

Why don't organisms like dolphins have the ability to breathe underwater, even though it would be advantageous?

All answers correct

In the case of the bentgrass population, why did the population on normal soils contain more tolerant genotypes than expected?

Pollen from plants on contaminated soils near mines carried alleles for heavy metal tolerance to the population on normal soils.

What is one major advantage of animal pollination?

It enhances outcrossing and avoids inbreeding.

How does pollination by animals benefit plants in tropical forests?

It allows for reproduction of plants that are widely dispersed.

What is the argument in support of a single origin for insect wings?

All answers correct.

Which insect order is an exception to the general patterns of thoracic musculature (indirect asynchronous muscles) and instead uses direct flight control muscles?

Odonata

Indirect control of flight means:

Instead of directly moving wings, the muscles contract and expand the thorax causing wing movement.

Paleoptery refers to "old wings" while neoptery refers to "new wings" that can fold tightly over the insect's body. Neoptery is important because:

all answers are correct

Insect stingers are made with modified:

ovipositors

Red dye (cochineal) is made of:

a bug that lives on cactus

What is a trophic cascade?

A series of changes in abundance and species composition across trophic levels due to changes at one level

How can omnivory (omnivores eat meat and plants) impact trophic cascades?

It buffers the effects of trophic cascades by consuming prey at multiple trophic levels

How does an increase in predation by a fourth trophic level (secondary level carnivore) on a third trophic level (first level carnivore) affect first trophic level primary producers (plants)?

It leads to a decrease in primary producers due to increased herbivory

In which type of ecosystem are trophic cascades hypothesized to be most important?

Simple, species-poor ecosystems

Why is measuring food web interaction strength important to ecologists?

It simplifies complex food webs by identifying the most important interactions

What challenges do ecologists face when trying to quantify every link in a food web?

All answers are correct

Ecology ch 21 What was the primary effect of removing the sea star Pisaster ochraceus from the experimental plots?

Mussels and gooseneck barnacles became dominant, reducing species diversity

What does the experimental removal suggest about the role of Pisaster ochraceus in the ecosystem?

It is a keystone species that helps maintain species diversity

Why are large oscillations in population size considered a sign of instability in a food web?

They increase the likelihood of species extinction

What is the primary function of decomposition in an ecosystem?

To release nutrients as soluble organic and inorganic compounds for uptake by other organisms

In decomposition of organic matter, what is mineralization?

The conversion of organic matter into inorganic nutrients by microorganisms

How does climate influence decomposition rates?

Warm temperatures and adequate moisture promote rapid decomposition

Hobbie video: What are two primary sources of nitrogen and phosphorus in the Como watershed?

Yard fertilizer and pet waste

Hobbie video: Which of the following statements about salt is true?

Salt has no natural way to be removed and requires source reduction.

In a study on pea aphids, why did the frequency increase of aphids with the bacterial symbiont Hamiltonella defensa?

Aphids with the symbiont survived at higher rates when wasp parasitoids were present

Why do hosts with heritable defensive symbionts tend to increase in frequency when parasites are common?

The hosts have higher survival and reproductive success than those without the symbiont

What initial control measures were attempted to reduce rabbit populations in Australia?

All answers are correct

How did rabbits affect the Australian ecosystem?

All answers are correct

Why did the myxoma virus become less effective over time in Australia?

Rabbits evolved resistance to the virus, and the virus evolved to become less lethal

Why do some parasites manipulate host behavior to increase the host's vulnerability to predators?

Because the predators are part of the parasite's life cycle, and the parasite needs to infect them

How can parasites alter predator-prey interactions

All answers correct

What are some general effects of parasitism on species interactions?

All answers are correct

What is a likely long-term outcome of host-parasite interactions in evolutionary terms?

A continuous evolutionary arms race, where the advantage shifts between host and parasite

What is the primary goal of using gene drives in Drosophila suzukii control?

To introduce genetic traits that lead to sterility or death

What are some of the ongoing harms caused by D. suzukii that gene drive and biological control aim to mitigate?

All answers correct

What are some risks associated with gene drive interventions in D. suzukii?

Hybridization with native Drosophilidae species and negative effects on D. suzukii populations in their native range

In Abram et al., how do gene drives differ from traditional biological control methods?

Gene drives involve genetic manipulation, while biological control uses natural enemies

Tait et al., where is spotted winged drosophila most likely to overwinter?

Wooded areas with abundant refuge and nutrients

Ecology Chapter 11, What environmental problem was already affecting the Black Sea when Mnemiopsis invaded?

Nutrient enrichment from sewage, fertilizers, and industrial waste

What is eutrophication?

An increase in the nutrient content of an ecosystem, leading to excessive plant and algae growth

Why is the Black Sea particularly vulnerable to nutrient enrichment?

limited water exchange and deep anoxic waters.

How did Mnemiopsis worsen the existing ecological problems in the Black Sea?

It consumed large quantities of zooplankton, leading to uncontrolled phytoplankton growth.

Why did oxygen levels in the Black Sea decrease after the Mnemiopsis invasion

Bacterial decomposition of dead phytoplankton and Mnemiopsis consumed oxygen.

What happens when a predator population initially lags behind its prey population?

Prey numbers increase rapidly.

What is a possible consequence of a high predator population and a low prey population?

Predator numbers decline due to food scarcity

Why do predator numbers sometimes fluctuate even after prey numbers have stabilized?

There is a time lag in predator reproduction and response to prey density.

What is the definition of a metapopulation?

A set of spatially isolated populations linked by dispersal

What is a "source" population in a metapopulation?

A population that sends more emigrants than it receives immigrants

What is a "sink" population in a metapopulation?

A population that receives more immigrants than it sends emigrants

In Nee and May, why might habitat destruction lead to an increase in the inferior competitor's patches?

The superior competitor is affected more by patch loss.

In Nee and May, how does habitat destruction relate to 'weedy' species?

Habitat destruction creates ecological changes that favor opportunistic species.

In Bahlai et al., between 2004 and 2006, what human intervention significantly altered the predator-prey dynamics between soybean aphid (Aphis glycines) and Asian ladybeetle (Harmonia axyridis)?

Widespread application of insecticides

Describe a metapopulation, use terms like patch, gene flow, source and sink, and stability

metapopulation: a group of spatially separated populations of the same species that live in different habitat patches but are connected by occasional movement of individuals among them.

• Each patch is an area of suitable habitat surrounded by unsuitable habitat. Some patches support strong, reproducing populations, while others are less favorable. Movement of individuals between patches creates gene flow, which helps maintain genetic diversity and can prevent small populations from becoming inbred or going extinct.

• Within a metapopulation, patches can function as sources or sinks:

• Source patches are high-quality habitats where local reproduction exceeds mortality, producing excess individuals that can disperse to other patches

• Sink patches are lower-quality habitats where local reproduction is not sufficient to maintain the population without incoming individuals from source patches.

• Stability of a metapopulation depends on the balance between local extinctions and recolonization of patches. Even if some patches experience extinction, the metapopulation can persist as long as dispersal allows empty patches to be recolonized and gene flow continues among patches.

Describe an insect biological control program, use terms like enemy release, host range, parasitoid, establish.

An insect biological control program involves introducing a natural enemy of a pest species to reduce its population, typically in areas where the pest has become invasive.

Many invasive insects become abundant because of enemy release, meaning they are no longer controlled by their natural predators, parasites, or pathogens from their native range. Without these controls, their populations can grow rapidly.

To manage this, scientists identify and introduce a natural enemy—often a parasitoid, which is an organism (commonly a wasp or fly) that lays its eggs in or on the pest insect. The developing offspring eventually kill the host.

Before introduction, the natural enemy's host range is carefully studied to ensure it targets only the pest species and does not harm non-target species. A narrow host range is preferred to reduce ecological risks.

After release, the goal is for the natural enemy to establish a self-sustaining population in the new environment. If it successfully establishes and spreads, it can provide long-term control of the pest by reducing its population and restoring ecological balance.

Describe a trophic cascade, use terms like carnivore, herbivore, plant.

A trophic cascade is an ecological process in which effects at one trophic level ripple through lower levels of a food web.

It typically begins with a carnivore, which preys on a herbivore. When carnivore populations are high, they reduce the abundance or alter the behavior of herbivores. This decreases the pressure that herbivores place on plants, allowing plant populations to increase or recover.

Conversely, if carnivores are removed or reduced, herbivore populations often increase, leading to heavier consumption of plants and a decline in plant biomass.

Thus, a trophic cascade describes how changes in carnivore populations indirectly affect herbivores and, in turn, the abundance and health of plants.

Describe biotic resistance, use terms like niche, competition, invasion, and co-evolution

Biotic resistance is the ability of a resident ecological community to limit the success of an invading species.

When a species attempts an invasion, it must occupy an available niche—the set of environmental conditions and resources it needs to survive and reproduce. In well-established communities, many niches are already filled, and resident species can strongly limit invaders through competition for resources such as food, space, or light.

Additionally, long-term co-evolution among native species can strengthen biotic resistance. Through co-evolution, species develop interactions such as effective predators, competitors, or pathogens that are well adapted to one another. These tightly linked relationships can make it difficult for a new species to establish because it lacks similar evolutionary adaptations.

As a result, strong competition and co-evolved interactions in a community can reduce the likelihood that an invading species will successfully establish and spread.

Describe the enemy release hypothesis, use terms like natural enemy, home range, biological control

The enemy release hypothesis explains why some species become invasive when they are introduced outside their native home range

In their home range, species are regulated by natural enemies such as predators, parasites, and pathogens that limit their population size. When individuals are transported to a new region, they often leave these natural enemies behind. Without this control, their populations can grow rapidly and spread, sometimes becoming invasive.

This idea is closely related to biological control, where scientists intentionally introduce a species' natural enemy from its home range into the invaded region to reduce its population. By reuniting the invasive species with its natural enemies, biological control aims to restore regulation and limit the invader's impact.

Describe ecosystem services, use terms like pollination, decomposition, population stability

Ecosystem services are the benefits that humans and other organisms receive from natural ecosystems. These services arise from the interactions among living organisms (plants, animals, microbes) and their physical environment, and they help sustain life on Earth.

For example, pollination is a key ecosystem service in which animals such as insects transfer pollen between plants, enabling plant reproduction and the production of fruits and seeds that humans rely on for food.

Another important service is decomposition, carried out by microbes and detritivores, which break down dead organic matter and recycle nutrients back into the soil. This process maintains soil fertility and supports continued plant growth.

Ecosystems also contribute to population stability by regulating species interactions such as predation, competition, and disease. These interactions help keep populations from becoming too large or too small, maintaining balance within ecosystems and supporting their long-term functioning.

Describe some ecological challenges of urban watersheds, use terms like storm sewers, impervious surfaces, pets.

Urban watersheds face several ecological challenges due to human development and land use changes.

One major issue is the presence of impervious surfaces such as roads, rooftops, and parking lots. These surfaces prevent water from soaking into the soil, increasing runoff. Instead of slowly infiltrating, water moves quickly across the surface and is funneled into storm sewers, which rapidly carry it into streams and rivers. This can lead to increased flooding, erosion, and the transport of pollutants.

Urban runoff often contains contaminants such as oils, heavy metals, fertilizers, and waste from pets. Pet waste is a significant source of nutrients and pathogens, which can degrade water quality and harm aquatic life.

Describe the brown food web, use terms like detritivore, scavenger, guild

The brown food web is the part of an ecosystem that is based on the consumption of dead organic matter (detritus), rather than living plant material.

It begins with detritus such as dead plants, animals, and waste products. Detritivores—organisms like earthworms and some insects—feed directly on this material, breaking it into smaller pieces and aiding in decomposition. Scavengers, such as vultures or other animals that consume dead organisms, also play a role by consuming larger carcasses.

These organisms can be grouped into a guild, meaning a set of species that use similar resources in similar ways—in this case, feeding on dead organic matter.

Describe the Nitrogen cycle, use terms like fertilizers, nitrogen fixation, and decomposition.

The nitrogen cycle describes how nitrogen moves between the atmosphere, soils, and living organisms, becoming available in forms that organisms can use.

Most nitrogen is found in the atmosphere as N₂ gas, which is not directly usable by most organisms. Through nitrogen fixation, specialized bacteria convert atmospheric nitrogen into ammonia (NH₃) or ammonium (NH₄⁺), forms that plants can take up. Humans also contribute to this process by producing fertilizers, which add large amounts of biologically available nitrogen to soils.

Plants assimilate this nitrogen and incorporate it into organic molecules such as proteins and nucleic acids. Animals then obtain nitrogen by consuming plants or other animals.

When organisms die or excrete waste, decomposition by microbes breaks down organic nitrogen back into ammonium in the soil. This can then be further transformed by other bacteria into nitrate (NO₃⁻), which plants can also use, or eventually converted back into atmospheric nitrogen through denitrification.