Ecology and Populations

 interactions between species (ex: predation, competition). This level examines how multiple species interact in the same area. These interactions influence biodiversity and species composition. For example, removing a predator can drastically change the entire community.

 energy flow and nutrient cycling between living and nonliving parts. Energy enters ecosystems through sunlight and moves through food webs. Nutrients cycle between organisms and the environment. This helps explain processes like carbon cycling and productivity.

exchange of energy, materials, and organisms across ecosystems.

 This focuses on how ecosystems are connected across larger areas. For example, rivers can act as corridors for species movement. Habitat fragmentation can disrupt these connections.

Distribution is limited by dispersal limits, behavior, biotic factors, and abiotic factors.

• Organisms may not reach an area due to physical barriers. Even if they arrive, they may not survive due to predators or unsuitable conditions. Multiple factors often interact to determine distribution.

studies species distribution over time, considering factors like climate change, evolution, and Earth’s history.

• helps explain why species are found in certain regions today.

major life zone defined by climate and dominant organisms, with temperature and precipitation shaping vegetation and life.

• large-scale ecosystems with similar climate and species. Climate, especially temperature and precipitation, determines vegetation. Disturbances like fire can shape biomes

Lakes/ponds, wetlands, streams/rivers, estuaries, intertidal, oceanic pelagic, coral reefs, marine benthic.

• defined by factors like salinity, depth, and light availability. Oceans cover about 75% of Earth’s surface. These systems are highly dynamic and influence global climate.

ropical forest, desert, savanna, chaparral, temperate grassland, taiga, temperate forest, and tundra, shaped mainly by climate patterns

• Each biome has unique adaptations in plants and animals.

Temperature, precipitation, sunlight, and wind determine long-term conditions and influence ecosystems and species distributions.

• Climate differs from weather because it reflects patterns over time. Global air circulation and solar energy influence these components.

Helps predict climate change effects, guide conservation, manage ecosystems, and understand habitat loss and species range shifts.

• Understanding distribution helps predict how species respond to warming climates. It helps protect endangered species.

use direct counts, sampling, extrapolation, and mark-recapture methods to estimate population size and density, especially for large or mobile species.

Estimate size using N = (S × n) / x, assuming equal capture chance and random mixing of marked individuals in the population.

• Method assumes organisms mix randomly and have equal capture chances. It is commonly used in wildlife studies. Ex- dolphins can be identified using dorsal fin patterns.

Dispersion patterns describe spacing of individuals: clumped, uniform, or random, often reflecting resource availability and species interactions.

 Study of population statistics such as birth rates, death rates, survival, and age structure.

• helps predict how populations will change over time. It is used in both ecology and human population studies. Factors like age structure strongly influence growth.

Dispersion patterns describe spacing of individuals: clumped, uniform, and random, influenced by resources and interactions.

Clumped dispersion occurs due to grouped resources or social behavior, where individuals cluster for food, shelter, or protection.

Uniform dispersion occurs when individuals are evenly spaced due to competition or territorial behavior for limited resources.

when environmental conditions are uniform and there is little interaction between individuals. It is the least common pattern in nature. This usually happens when resources are evenly distributed.

Population growth depends on birth rate (b) and death rate (m), which determine whether populations increase or decrease.

• For example, limited food can reduce births and increase deaths.

Formula: r = b − m

•  If r is positive, the population grows; if negative, it declines. When r equals zero, the population is stable. This formula is foundational for understanding population dynamics.

age-specific surival data for a population

•  track survival rates at different ages. They help identify which life stages have the highest mortality. This information is useful for conservation and population management.

can vary by age, environment, and species. High mortality in early life stages is common in many organisms. Understanding mortality helps predict population trends.

• indicates how many individuals make it to the next age group. It is often used in life tables. High survival rates usually lead to population growth.

• describes how mortality is distributed across ages. Different species show different survivorship patterns. These patterns reflect evolutionary strategies.

• pattern showing survival across lifespan

  • graphs how many indivudals survive at each age. They help visulize life histroy strateigeis.

• Three types - 1, II, III

• low death rate during early and middle life and increase in death in older age groups

• surivve to old age and is more common in species with parental care. Investment in fewer offspirng increase surival early in life

equal chance of dying at any age (ex. squirrels)

• resultts in a straight line decline in suiviorship. Many birds and animals show this pattern

High earrly mortality

• many die young but surviors live long lives. Hence, species produce offspring with lttle parental care

• strategy meant to increase chances that some will survive.

shows age-specific reporduction (offspring number, breeding rates)

• table show which age groups contribute most to reproduction. Helps predict future poulation growth. Often compbined with life tables for analysis

helps predict population growth and reproductive success

• idetifying peak reproductive ages helps in conservation planning. Ex - protecting breeding adults can stablize populations. Also helps manage wildlife populations

group of indiviudals of same age.

• are tracked overtime to study survival and reproduction. Essential for contrsucting life table.

• allows for ecologist to analyze population changes across generations

predicts population trends  (more young → growth, more old → decline).

• Age structure affects future population size. A population with many young individuals is likely to grow rapidly. In contrast, older populations may decline over time.

traits affecting survival and reproduction, shaped by natural selection

• include when reproduction begins and how many offspring are produced. These traits evolve to maximize fitness. Different environments favor different strategies.

Age at reproduction, frequency, number of offspring, and trade-offs between survival and reproduction

•  Organisms must balance energy between growth, survival, and reproduction. Producing many offspring may reduce survival chances. These trade-offs shape evolutionary strategies.

reproduce once

•  strategy is common in unstable environments. Organisms invest all energy into one reproductive event. Examples include agave plants.

reproduce mutiple times

• strategy is favored in stable environments. Organisms spread reproduction over time. Humans are an example of iteroparous species.

Rapid J-shaped increase under ideal conditions (unlimited resources)

• occurs when resources are abundant. Populations increase rapidly without limits. It is rarely sustained in natural environments.

r = growth rate, N = population size, t = time.

•  These variables are used in population growth models. They help describe how populations change over time. Understanding them is key to predicting growth patterns.

ocurs when conditions are very favorable

• may happen after distubrances or when species enters new enviroment. Ex - procted species can increase rapidly however grwoth eventually slows due to natural limiations

Births = deaths

• population size remains stable. It often occurs when resources are limited. Many populations fluctuate around this balance.

Logistic growth = S-shaped, slows as resources become limited

• Growth starts rapidly but slows as population size increases. This reflects environmental resistance. Most natural populations follow this pattern.

K = carrying capacity, max population the environment can sustain

•  Carrying capacity depends on available resources. It can change over time with environmental conditions. Populations tend to stabilize around this value.

Occurs when resources are limited and density increases.

•  As population density increases, competition and other factors slow growth. This creates a balance between growth and resource availability. It is the most common growth pattern in nature.

r-selection many offspring, early reproduction → unstable environments

K-selection fewer offspring, competitive traits → stable environments

•  r-selected species grow quickly /exploit temporary resources. K-selected species invest more in fewer offspring. Strategies reflect environmental stability.

Competition, disease, predation, waste buildup lower birth rates and increase death rates.

• These are density-dependent factors that increase with population size. They help stabilize populations around carrying capacity. Without them, populations would grow uncontrollably

Farmers use it to control pests and crop yield; conservationists use it to predict extinction risk and manage species

• Example, very small populations like the northern white rhinoceros are high risk