Exam 4 Flashcards by ashley martinez

Define population

A group of interbreeding organisms of the same species in one location at a specific time.

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Define community

All interacting populations of various species in an area.

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Define ecosystem

The community of organisms plus their non-living environment (air, water, minerals).

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Define ecology

The study of interactions between organisms and their environment

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What are the key measurements used to study populations?

Population size: Total number of individuals.
Population density: Individuals per unit area/volume.
-Formula: Density=Populationsize/Area
Population distribution: Patterns of how individuals are spaced (random, uniform, clumped).
Population dynamics: Study of factors affecting size changes (births, deaths, immigration, emigration).

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What are the three types of population distribution, and what causes each?

Clumped: Individuals group where resources are abundant or for protection/reproduction.
Uniform: Even spacing due to territoriality or competition.
Random: Unpredictable spacing in uniform habitats with no strong interactions.

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How do you calculate population growth rate using the formula 𝐺=𝑟𝑁?

G: Growth rate (individuals added per time unit).
r: Per capita growth rate (rate of increase per individual).
N: Total population size.
Example: If 𝑟=0.1 and 𝑁=500, then 𝐺 = 0.1×500=50 individuals added.

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Differentiate between exponential and logistic growth.

Exponential growth:
𝐺=𝑟𝑁, produces a J-shaped curve; occurs in ideal, unlimited environments but is unsustainable.
Logistic growth: Growth slows as resources become limited, producing an S-shaped curve; stabilizes at carrying capacity (K).

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What are density-dependent and density-independent factors in population control?

-Density-dependent (biotic): Factors like competition, predation, and disease; impact increases with population density.
-Density-independent (abiotic): Factors like natural disasters or habitat destruction; affect populations regardless of size.

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What are the life history strategies of K-selected and r-selected species?

K-selected species: Thrive in stable environments.
-Traits: Larger size, fewer offspring, lots of -parental care.
-Example: Elephants, humans.
r-selected species: Thrive in unpredictable environments.
-Traits: Smaller size, lots of offspring, little to no parental care.
-Example: Insects, fish.

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What are semelparity and iteroparity in reproduction?

Semelparity: Organisms reproduce once in their life, producing many offspring at once.
-Traits: No parental care, high energy use.
-Example: Salmon, agave plants.
Iteroparity: Organisms reproduce multiple times during their life.
-Traits: Parental care provided, offspring survive longer.
-Example: Birds, humans.

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What are the three types of survivorship curves, and what do they mean?

Type I: Most survive to old age, then die (high parental care).
-Example: Humans, elephants, whales
Type II: Death happens steadily over time, at any age.
-Example: Birds, rodents, turtles
Type III: Many die young, but survivors live a long time (no parental care).
-Example: Fish, insects, marine invertebrate

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How do predator-prey relationships create population cycles?

-When prey increases, predators have more food, so predator numbers grow.
-High predator numbers then lower prey populations.
-With less food, predator numbers drop, allowing prey to recover.

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What are density-dependent and density-independent factors?

Density-dependent factors: Depend on how many individuals are in the population.
-Examples: Competition for food, disease, predation.
Density-independent factors: Happen no matter the population size.
-Examples: Natural disasters, pollution.

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How do resources and social interactions influence population distribution?

Clumped: Individuals group together where resources are available or for protection/reproduction.
Uniform: Individuals spread evenly due to competition or territoriality.
Random: No predictable pattern; happens in uniform environments without strong social interactions.

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What is carrying capacity (K), and how does it affect population growth?

-Carrying capacity (K): The largest population an environment can support with its resources.
-Effect: Growth slows down as the population approaches K because resources become limited.

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Why can exponential growth not continue forever?

-Resources (like food and space) eventually run out.
-This leads to competition, slower growth, and possibly population decline.

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What is environmental resistance, and how does it affect populations?

Environmental resistance includes all the factors that limit population growth, like limited food, competition, disease, and predators. It keeps populations in check.

What is a population oscillation, and what causes it?

Populations rise and fall over time, often due to predator-prey dynamics. Prey populations grow, predators follow, prey decreases, and the cycle repeats.

What happens when a population exceeds its carrying capacity?

The population overuses resources, leading to starvation, disease, or habitat damage. Eventually, the population crashes or stabilizes at a lower level.

Why do clumped distributions dominate in nature?

-Resources are unevenly distributed in their favor
-Grouping provides safety, easier mating, and better access to resources (e.g., schools of fish or lion prides).

What is a community in ecology?

A community consists of all populations of different species that interact in a specific area.

What are the three types of symbiotic relationships?

-Mutualism (+/+): Both species benefit (e.g., clownfish and sea anemones).
-Commensalism (+/0): One species benefits, and the other is unaffected (e.g., moss on trees).
-Parasitism (+/-): One species benefits, and the other is harmed (e.g., ticks on mammals).

What is the Competitive Exclusion Principle?

Two species competing for the same limited resource cannot coexist indefinitely; one species will outcompete the other.

What is resource partitioning, and why is it important?

Resource partitioning is when species divide resources to minimize competition, allowing similar species to coexist.

What’s the difference between a fundamental niche and a realized niche?

-Fundamental niche: The full range of resources a species could use without competition. -Realized niche: The actual range used when competition or other interactions occur.

What are two types of mimicry used by prey?

-Batesian mimicry: Harmless species mimic harmful ones (e.g., a harmless fly resembling a wasp). -Müllerian mimicry: Harmful species share similar warning signals (e.g., toxic butterflies with the same coloration).

What are some common prey defenses?

-Coloration: Camouflage or warning colors. -Physical defenses: Spines, shells, or pincers. -Chemical defenses: Toxins or noxious chemicals (e.g., poison dart frogs).

What is a keystone species?

A species with a disproportionate effect on community diversity. Removing it can drastically reduce diversity (e.g., sea otters controlling sea urchin populations).

What is ecological succession?

-Primary succession: Occurs in lifeless areas (e.g., after lava flow). -Secondary succession: Happens in disturbed areas where soil remains (e.g., after a forest fire).

What is the Intermediate Disturbance Hypothesis?

Ecosystems with moderate disturbance levels have the highest diversity because they balance dominant species and slower-growing ones.

What are the levels of a food chain?

1. Primary producers (autotrophs): Use sunlight to make energy (e.g., plants). 2. Primary consumers: Eat producers (e.g., herbivores). 3. Secondary and tertiary consumers: Eat other consumers (e.g., carnivores). 4. Decomposers: Break down organic matter (e.g., fungi, bacteria).

Why is energy transfer between trophic levels inefficient?

Only ~10% of energy is transferred to the next level; the rest is lost as heat or used for maintenance.

What are biogeochemical cycles, and why are they important?

They recycle nutrients like carbon, nitrogen, and phosphorus through biotic and abiotic systems, ensuring ecosystem sustainability.

What role do bacteria play in the nitrogen cycle?

-Nitrogen fixation: Convert N₂ into usable forms like ammonium (NH₄⁺). -Nitrification: Convert ammonium into nitrates (NO₃⁻). -Denitrification: Return nitrogen to the atmosphere as N₂.

What is eutrophication, and why is it harmful?

Eutrophication happens when too much nitrogen or phosphorus enters an ecosystem, causing algae blooms. These blooms block sunlight and reduce oxygen, harming aquatic life.

How does deforestation impact the water cycle?

Deforestation reduces transpiration, leading to less rainfall, more runoff, and drier ecosystems.

What is the greenhouse effect, and why is it important?

The greenhouse effect keeps Earth warm by trapping heat from the sun in the atmosphere using gases like CO₂ and methane. However, excess greenhouse gases from human activities cause global warming.

How do CO₂ emissions affect global temperatures?

Higher CO₂ levels trap more heat in the atmosphere, causing global temperatures to rise. This leads to ice melting, sea levels rising, and more extreme weather patterns.

How is the phosphorus cycle unique?

Unlike nitrogen or carbon, phosphorus does not cycle through the atmosphere. It moves from rocks into soil and water, where it is taken up by plants, passed to animals, and returned to the soil through decomposition.

How does the carbon cycle work in ecosystems?

Plants absorb CO₂ during photosynthesis and use it to make organic matter. Animals consume plants, transferring carbon. Decomposers return carbon to the atmosphere as CO₂ or store it in soil.

What is nitrogen fixation, and why is it important?

Nitrogen fixation is when bacteria convert nitrogen gas (N₂) from the atmosphere into ammonium (NH₄⁺) or nitrate (NO₃⁻), making nitrogen available to plants for growth.

What are limiting nutrients, and why do they matter?

Limiting nutrients, like nitrogen or phosphorus, are essential for plant growth but are in short supply. Adding them can boost productivity, but too much can cause problems like eutrophication.