Population Ecology

Population Ecology

• Population is a group of individuals of the same species occupying the same environment
• Three key population features include size, range, and density
• A community comprises different species living together, interacting through predation, competition, and symbiosis
• An ecosystem encompasses all biotic (living) and abiotic (non-living) components in an area

Exponential and Logistic Growth Models

• Exponential growth models apply to populations with no growth limits, utilizing biotic potential
• Logistic growth models apply to populations approaching their carrying capacity
• Exponential growth lacks carrying capacity, allowing unconstrained population growth
• Logistic growth allows population growth until it reaches its maximum, where the growth rate slows

r and K Strategists

• r-strategy species traits maximize reproductive success in uncrowded environments
• K-strategy species traits maximize fitness in crowded environments
• R-strategists have a type 3 survivorship curve, early reproduction, many offspring, short life span, little parental care, one reproduction event, and small adult size; they are prey below carrying capacity
• K-strategists have type 1 and 2 survivorship curves, late reproduction, few offspring, long life span, much parental care, multiple reproductions, and large adult size; they are predators near carrying capacity

Factors Causing Population Decrease

• Changes to birth and death rates decrease population
• High death rate or low birthrate
• Limited resources like food, water, and shelter
• Climate change, such as rising temperatures
• Disease/epidemics, such as white-nose syndrome in bats

Photosynthesis Purpose and Products

• Photosynthesis converts light energy into chemical energy, powering life with the sun's rays
• The products of photosynthesis are glucose and oxygen

Importance of Photosynthesis

• Photosynthesis makes food and adds oxygen to the atmosphere

Food Chains/Webs and Trophic Levels

• 1st level: producers (plants, algae, grass) make their own food through photosynthesis or chemosynthesis; they are the foundation of the food web
• 2nd level: primary consumers (grasshoppers, bees, ants, butterflies) are herbivores that eat producers
• 3rd level: secondary consumers (rats, sparrows, frogs) are carnivores or omnivores eating primary consumers
• 4th level: tertiary consumers (snakes, owls) are carnivores eating secondary consumers; they are top predators with few natural predators
• Decomposers (fungi, bacteria) and detritivores (earthworms, scavengers) are also important, but not trophic levels
• 90% of energy is lost as it passes through the trophic levels

Metabolic Categories

• Photoautotrophs: use light energy with carbon dioxide as the carbon source (e.g., cyanobacteria, plants, algae)
• Photoheterotrophs: use light energy with organic compounds as the carbon source (e.g., purple nonsulfur bacteria)
• Chemoautotrophs: use inorganic compounds (NH3 & H2S) as the energy source and CO2 as the carbon source (e.g., purple sulfur bacteria)
• Chemoheterotrophs: use organic compounds for both energy and carbon (e.g., fungi, animals, most bacteria)

Human Population Growth

• Reduced death rate, public health changes, infectious disease impacts, and technological advances have contributed to human population growth
• Rapid growth occurs in countries with pyramid-shaped age structure diagrams and young demographics
• Stable populations have dome-shaped age structures with even distribution across age groups
• Declining populations have inverted pyramid-shaped structures with more elderly

Biomes

• Tropical rainforests have stable temps (20-34°C), yearlong growing season, high rainfall (50-200 inches), high biodiversity, and productivity
• Savannas are tropical/subtropical grasslands with moderate, seasonal rainfall, transitional between forests and deserts with widely spaced trees and seasonal migrations
• Chaparral (scrub forest) has annual rainfall (25.6-29.5 inches), mostly in winter; vegetation is dominated by shrubs adapted to periodic fires
• Deserts have unpredictable, little precipitation, temps fluctuate (60°C day, 0°C night); vegetation is sparse and adapted for water conservation

Biomes Part 2

• Temperate Grasslands (prairies/steppes) have seasonal temps, less precipitation than savannas, deep fertile soil, seasonal migration, and fires
• Temperate forests have mild, seasonal climates with plentiful rain (29.5-59 in), soil rich in organic material, and deciduous trees; biodiversity is diminished by human activity
• Taiga (Boreal Forest) has harsh winters, cold/dry winters, short/cool/wet summers; evergreen trees are adapted for the cold, with limited precipitation, mostly in winter
• Tundra is above the taiga, below the poles, with low precipitation, open windswept areas, permafrost, and low species richness

Aquatic Biomes

• Freshwater covers only 2% of Earth, provides drinking water, crop irrigation, sanitation, and habitat
• Marine (salt water) is influenced by light levels, temps, tides, and currents; primary producers are phytoplankton and rooted plants in photic zones; 3 ocean ecosystems: open ocean, continental shelves, deep sea

Community Ecology

• Ecological niche is the total ways a species uses resources and impacts its environment, including space, food, abiotic parameters, mating conditions, and ecosystem role

Ecological Succession

• Succession produces a change in species composition over time
• Primary succession begins with a barren, lifeless substrate
• Secondary succession is in an existing community that has been disturbed

Competitive Exclusion

• Competitive exclusion: The species better able to utilize a shared niche will eliminate the other (survival of the fittest)
• Resource partitioning: Is the division of niches that allow for coexistence. Temporal, morphological, and spatial.

Symbiosis Types

• Mutualism benefits both species
• Antagonism is where one or both parties lose more than they gain and is classified as competition, predation or parasitism
• Commensalism benefits one species and is neutral to the other

Example Predation and Adaptations

• Monarch butterflies consume milkweed and as a result, the monarch butterflies themselves are toxic to birds

Biodiversity

• Bacteria: prokaryotic; cells lack organelles, single-celled, found in all ecosystems
• Archaea: prokaryotic; are extremophiles
• Eukarya: multicellular or single-celled, have a nucleus
• Protists: not fungus, plant, or animal; usually single-celled
• Fungi: multicellular or single-celled; heterotrophic
• Plants: multicellular; photoautotrophs; perform photosynthesis
• Animals: multicellular; heterotrophic

Endemic Species

• Endemic species are found in only one geographical area
• Disruption of ecosystem interactions, pollution and loss of genetic variation can impact biodiversity loss
• Solutions to biodiversity loss include changing human behavior, habitat conservation and restoration

Example of Natural Selection

• Galapagos finches have beak size variations, some finches have long, strong beaks and others had smaller, more delicate beaks
• The weather and environment, determines which finches will be more suitable
• Over generations, finches with beak size that were suitable for the climate would survive and reproduce with the same trait