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Photosynthesis

The process by which plants use light, carbon dioxide, and water to produce glucose and oxygen.

Auto-trophs

Organisms, like plants, that produce their own food from sunlight through photosynthesis.

Net Primary Productivity (NPP)

The difference between carbon gained via photosynthesis and carbon lost through respiration.

Stomata

Small openings on the surface of leaves that allow the exchange of gases.

C3 Photosynthesis

A common form of photosynthesis where Rubisco enzyme captures CO2, but risks photorespiration at high temperatures.

C4 Photosynthesis

A form of photosynthesis that minimizes photorespiration by using PEP carboxylase to capture CO2.

CAM Photosynthesis

A water-conserving process where stomata open at night to take in CO2 and close during the day.

Microphylly

The adaptation of plants to have very small leaves to reduce water loss in dry environments.

Evaporative Cooling

The cooling effect that occurs when water evaporates from leaf surfaces.

Deciduous Habit

The characteristic of some plants to shed leaves during dry or cold seasons to conserve water.

Morphological Plasticity

The ability of a plant to change its structure in response to environmental conditions.

Epiphytes

Plants that grow on other plants for support but do not extract nutrients from them.

Root Foraging

The behavior of roots searching for nutrients and symbiotic bacteria in the soil.

Trade-off

A situation where gaining one benefit requires the loss of another, such as between growth rate and water conservation.

Convergent Evolution

The independent evolution of similar traits in different species due to adaptation to similar environments.

Rubisco

An enzyme key to C3 photosynthesis, responsible for fixing carbon dioxide, but prone to photorespiration at high temperatures.

PEP carboxylase

An enzyme used in C4 and CAM photosynthesis to efficiently capture carbon dioxide, especially at lower concentrations, minimizing photorespiration.

Photorespiration

A process in plants, particularly in C3 photosynthesis, where the enzyme Rubisco binds with oxygen instead of carbon dioxide, reducing photosynthetic efficiency, especially in hot conditions.

Respiration

The process by which organisms convert glucose and oxygen into energy, releasing carbon dioxide and water as byproducts, which contributes to carbon loss in plants.

Xerophytes

Plants adapted to survive in arid (dry) environments, often exhibiting features like thick cuticles, sunken stomata, or succulence.

Succulence

An adaptation in plants where they have fleshy stems, leaves, or roots to store water, common in desert plants like cacti.

Cuticle

A waxy, protective layer on the surface of plant leaves and stems that helps to prevent water loss through evaporation.

Chlorophyll

The primary green pigment in plants that absorbs light energy, especially in the red and blue spectrums, to power photosynthesis.

Chloroplasts

Organelles found in plant cells and other eukaryotic photosynthetic organisms, where photosynthesis takes place.

Light-Dependent Reactions

The first stage of photosynthesis, occurring in the thylakoid membranes of chloroplasts, where light energy is captured to produce ATP and NADPH.

Calvin Cycle (Light-Independent Reactions)

The second stage of photosynthesis, occurring in the stroma of chloroplasts, where carbon dioxide is fixed and converted into glucose using the ATP and NADPH produced during the light-dependent reactions.

Population Dynamics

The study of how population size changes through time.

Population Size (N)

The number of individuals in a population.

Population Density

The number of individuals per unit area.

Exponential Growth

Population growth where the number of individuals grows at a constant rate over time.

Geometric Growth

A model describing population growth in discrete time periods, characterized by a constant growth factor.

Density Dependence

Population growth regulation based on the population size, often due to limited resources.

Logistic Growth Model

A model that describes population growth that is restricted by carrying capacity, resulting in an S-shaped curve.

Carrying Capacity (K)

The maximum population size that an environment can sustain.

Intrinsic Rate of Increase (r)

The rate at which a population would grow without any limiting factors.

Per-Capita Rate

The rate of birth or death per individual in the population.

Malthusian Theory

The theory that population growth is limited by food production and will eventually reach carrying capacity.

Paul Ehrlich's Population Bomb

A book arguing that explosive human population growth would lead to catastrophic consequences.

Sigmoid Growth Curve

The characteristic S-shaped curve produced by the logistic growth model.

Density-Independent Factors

Environmental factors that affect population size regardless of the population's density.

Mortality (D)

The number of individuals that die within a population during a specific time interval.

Fecundity (B)

The number of births or individuals added to a population during a specific time interval.

What is the mathematical equation for population change?

\Delta N = B - D

Or

\frac{dN}{dt} = rN

What is the mathematical equation for exponential growth?

\frac{dN}{dt} = r\_{max}N

What is the mathematical equation for logistic growth?

\frac{dN}{dt} = r\_{max}N\left(\frac{K-N}{K}\right)

What is the per-capita growth rate (r) equal to?

r = b - d

Where b is per-capita birth rate and d is per-capita death rate.

Provide examples of density-dependent factors affecting population growth.

• Resource availability (food, water, shelter)
• Predation
• Competition (intraspecific and interspecific)
• Disease transmission
• Waste accumulation

Provide examples of density-independent factors affecting population growth.

• Natural disasters (floods, fires, earthquakes)
• Extreme weather conditions (droughts, severe cold)
• Pollution
• Habitat destruction (human-caused)

What happens to the population growth rate as population size (N) approaches carrying capacity (K) in the logistic growth model?

The population growth rate slows down as N approaches K because the (\frac{K-N}{K}) term in the logistic equation approaches zero.

Carrying Capacity (K)

The maximum population size that an environment can sustain.

Logistic Growth

Population growth that begins exponentially but slows as the population approaches carrying capacity.

Intrinsic Rate of Increase (r)

The rate at which a population would grow if there were no limits to its growth.

Malthusian Theory

The theory stating that population growth is constrained by food production limits.

Paul Ehrlich

Author of The Population Bomb, warning about the consequences of rapid population growth.

Sigmoid Growth Curve

The S-shaped curve representing logistic growth over time.

Birth Rate and Death Rate

The rates at which individuals are added to or removed from a population.

Per-Capita Rates

Rates calculated based on the individual contribution to population growth or decline.

Age-structured population

A population divided into distinct age groups to analyze how age-specific rates of birth, death, and reproduction influence overall population dynamics. These models are crucial for predicting population trends, informing resource management, and detecting age-specific vulnerabilities.

Life table

A summary of age-specific survival and reproductive rates within a population. Key components include: age class (x), survivorship (l\x), age-specific mortality (d\x), age-specific mortality rate (q\x), and age-specific fecundity (m\x). Life tables can be cohort (following a group) or static (sampling at a specific time).

Fecundity

The reproductive capacity of an organism, typically referring to age-specific fecundity (m\x), which is the average number of female offspring produced by a female of age x. It's vital for calculating R\0 and T.

Survivorship curve

A graph plotting the proportion of individuals surviving at each age (l\_x vs. x). There are three main types:

1. Type I (Concave): High survival until old age (e.g., humans).
2. Type II (Diagonal): Constant mortality rate throughout life (e.g., some birds).
3. Type III (Convex): High mortality for the young, high survival for those reaching maturity (e.g., many insects).

Semelparity

A reproductive strategy where an organism has a single, often large, reproductive event followed by death (e.g., Pacific salmon). This is common in unpredictable environments.

Iteroparity

A reproductive strategy involving repeated reproductive events over an organism's lifespan (e.g., humans). This is favored in stable environments where adults have a high chance of surviving to reproduce again.

Allee effect

A phenomenon where individual fitness and population growth rate decrease at low population densities. This can be due to difficulties in mate finding, reduced cooperative benefits, or genetic problems, posing a risk of extinction.

Net reproductive rate (R\_0)

The average number of female offspring produced by a female in her lifetime, calculated as the sum of (l\x \times m\x). If R\0 > 1, the population is growing; if R\0 = 1, it's stable; if R\0 < 1, it's declining. \qquad R\0 = \sum\{x=0}^{\omega} l\x m\_x

Generation time (T)

The average age of mothers in a cohort when they give birth, representing the average time between generations. Shorter generation times lead to faster population growth. It can be estimated by: \qquad T = \frac{\sum\{x=0}^{\omega} x l\x m\x}{R\0}

K strategy

A life history strategy for stable environments, characterized by slow development, long lifespan, large body size, few large offspring, high parental investment, and density-dependent selection (e.g., elephants).

r strategy

A life history strategy for unpredictable environments, characterized by rapid development, short lifespan, small body size, many small offspring, low parental investment, and density-independent selection (e.g., bacteria, insects).

Life expectancy (e\_x)

The average number of additional years an individual of a given age x is expected to live, calculated from life tables.

Reproductive value (v\_x)

The expected contribution of an individual of age x to future population growth, considering current and future reproductive output and survival probabilities. It helps prioritize conservation efforts.

Survivorship schedule (l\_x)

A component of a life table detailing the proportion of an initial cohort still alive at the beginning of each age interval x, measuring the probability of surviving from birth to age x.

Fecundity schedule (m\_x)

A component of a life table specifying the average number of female offspring produced per female during a particular age interval x. It's crucial for calculating R\_0.

Trade-offs in reproduction

The allocation of limited energy and resources by an organism among competing demands like growth, maintenance, and reproduction. Key trade-offs include current vs. future reproduction, number vs. size of offspring, and parental care vs. offspring number.

Population Growth Models

Mathematical frameworks to predict how population size changes over time.

1. Exponential Growth: Occurs with unlimited resources (J-shaped curve). Formula: \frac{dN}{dt} = rN or Nt = N0 e^{rt}.
2. Logistic Growth: Accounts for environmental limits (carrying capacity K) (S-shaped curve). Formula: \frac{dN}{dt} = rN(1 - \frac{N}{K}).

Intrinsic rate of natural increase (r)

The maximum potential per capita rate of population growth under ideal conditions. A higher r indicates a faster-growing population. It can be approximated by: \qquad r \approx \frac{\ln(R\_0)}{T}

Density-dependent factors

Factors that limit population growth more strongly as population density increases, intensifying with crowding. These are usually biotic (e.g., competition, predation, disease) and regulate population size towards K.

Density-independent factors

Factors affecting population growth regardless of density. These are typically abiotic (e.g., natural disasters, extreme weather, pollution) and can cause population fluctuations but don't regulate towards K.

Life History Traits

A set of characteristics influencing an organism's survival and reproduction, shaped by natural selection through evolutionary trade-offs. Key traits include age at first reproduction, offspring number/size, reproduction frequency, lifespan, and parental care.

Mortality rate (q\_x)

The probability that an individual alive at the beginning of an age interval x will die during that interval. Calculated as deaths (d\x) divided by individuals alive at the start (n\x): \qquad q\x = \frac{d\x}{n\_x}

Community Ecology

The study of interactions among species in a community, focusing on the dynamics of species interactions, competition for resources, and the overall structure and function of ecological communities. It investigates how different species coexist, interact, and influence each other's populations and distributions.

Intra-specific Competition

Competition that occurs among members of the same species for limited resources such as food, water, light, mates, or territory. This competition can regulate population size and influence individual fitness, often leading to natural selection.

Inter-specific Competition

Competition that occurs among members of different species for shared, limited resources. This type of competition can lead to competitive exclusion, resource partitioning, or character displacement, affecting the distribution and abundance of competing species.

Lotka-Volterra Model

A mathematical model that describes the dynamics of biological systems in which two species compete for the same resources. It uses differential equations to predict population sizes over time, considering intrinsic growth rates, carrying capacities, and competitive effects of each species on the other.

Competitive Exclusion Principle

Also known as Gause's Law, this principle states that two species competing for the exact same limited resources in the same niche cannot stably coexist. One species will eventually outcompete and eliminate the other, or they will evolve to specialize or partition resources.

Competitive Coefficients (\alpha and \beta)

Measures used in the Lotka-Volterra model to quantify the effect of one species on another in terms of their resource consumption. For example, competitive coefficient \alpha\_{12} represents the per capita effect of species 2 on species 1, essentially converting individuals of species 2 into equivalent individuals of species 1 in their competitive impact.

Exploitative Competition

An indirect form of competition that occurs when one species consumes or uses a shared resource, thereby reducing its availability for another species. The competing individuals do not directly interact; their interaction is mediated solely by the shared resource.

Interference Competition

A direct form of competition that occurs when individuals interact aggressively or through other direct means to prevent others from accessing resources. This can involve fighting, territorial defense, or producing chemicals that inhibit competitors.

Paradox of the Plankton

The observation by G. Evelyn Hutchinson that numerous phytoplankton species can coexist in seemingly homogeneous aquatic environments despite competing for the same limited resources (e.g., light, nutrients). This challenges the Competitive Exclusion Principle, suggesting that environmental fluctuations, predation, or spatial heterogeneity might prevent competitive exclusion.

Character Displacement

An evolutionary process where differences in morphological, physiological, or behavioral traits among similar species are accentuated in areas where they co-occur. These exaggerated differences reduce inter-specific competition and facilitate coexistence by allowing species to utilize resources differently.

Stability in Ecology

The ability of an ecological community to maintain its structure, composition, and function over time, especially in the face of disturbances. It encompasses concepts like resistance (ability to resist change) and resilience (ability to recover after disturbance).

Species Richness

A direct measure of biodiversity, representing the total number of different species present in a particular community, habitat, or ecosystem. It is a fundamental component of community structure.

Community Composition

The identity of the species present within a community, along with their relative abundances. It describes which species are found there and how common each of them is, providing a detailed picture of the community's biological makeup.

Scramble Competition

A form of exploitative competition where individuals do not interact directly. Instead, they equally share a limited, divisible resource, and if the resource runs out, all individuals may suffer equally, potentially leading to reduced growth, reproduction, or survival for all.

Contest Competition

A form of interference competition characterized by direct aggressive interactions such as fighting, territorial defense, or establishment of dominance hierarchies over resources. In this type, winning individuals obtain sufficient resources, while losing individuals get little or none.

Coexistence

The state in which multiple species persist together in the same ecological community over extended periods without one outcompeting or excluding the others. Mechanisms enabling coexistence include resource partitioning, character displacement, predation, and environmental heterogeneity.

Asymmetrical Competition

A type of competition where the detrimental impact of the competition is unequal among the species involved. One species experiences a much greater negative effect than the other, often due to differences in competitive ability, resource needs, or body size.

Niche

The specific role an organism plays within its ecosystem, encompassing all its interactions with the biotic and abiotic factors of its environment, including resource use, habitat, and interactions with other species.

Fundamental Niche

The full range of environmental conditions and resources that a species can possibly use and tolerate in the absence of competitors, predators, or other limiting factors.

Realized Niche

The actual range of environmental conditions and resources that a species utilizes in the presence of competitors, predators, and other factors that restrict its distribution and abundance. It is often smaller than the fundamental niche.

Resource Partitioning

The process by which species divide shared resources in a way that minimizes competition. This can occur through differences in resource use (e.g., different food types, feeding times, or foraging locations) or by exploiting resources at different life stages, allowing them to coexist.