Botany Exam 4

Ecology and Plant Ecology

• Ecology: The study of interactions between organisms and their environment.

• Plant Ecology: Explains how plants interact with each other, their environment, and how they adapt to environmental factors.

Levels of Ecology

1. Organismal Ecology/Autecology: Studies individual organisms and their adaptations to environmental factors.

   • Example: How a cactus survives in desert conditions.

2. Population Ecology: Examines populations of a species, their size, distribution, and interactions.

   • Example: A group of deer in a forest.

3. Community Ecology: Studies the interactions among different species in an area.

   • Example: The interaction of plants, animals, and microorganisms in a forest.

4. Ecosystem Ecology: Focuses on energy flow and nutrient cycling within ecosystems.

   • Example: A wetland ecosystem with water, plants, and animals interacting.

5. Landscape Ecology: Examines patterns across large landscapes and how ecosystems interact.

   • Example: The transition from a forest to a grassland.

6. Biosphere Ecology: Studies the global processes that affect life on Earth.

   • Example: The effects of climate change on plant species worldwide.

Organismal Ecology

• Abiotic vs. Biotic Factors:

  • Abiotic: Non-living factors (e.g., temperature, light, soil).

  • Biotic: Living factors (e.g., competition, predation).

• Factors Affecting Plants:

  • Light: Plants need light for photosynthesis.

  • Water: Availability of water affects plant growth.

  • Nutrient Availability: Essential for growth and reproduction.

  • Soil Texture: Affects water retention and root growth.

• Other Abiotic Factors:

  • Latitude: Affects temperature, sunlight, and seasons.

  • Elevation: Affects temperature and air pressure.

    • Timberline and alpine zones are at high elevations with extreme conditions.

  • Disturbance: Natural events like fires or storms can alter plant habitats.

  • Plant Impact on Habitat: Plants can affect light, water, and nutrient availability, altering their habitat.

Population Ecology

• Population Ecology: Studies the distribution and abundance of populations, and how factors like competition and resources influence them.

• Intraspecific Competition: Competition within the same species for resources (e.g., light, space).

• Self-Thinning: When plants in a crowded population die off to reduce competition.

• Facilitation: When one species benefits another (e.g., plants providing shade).

• Species Ranges: The geographic areas where species live, influenced by factors like climate and soil.

  • Disjunct Distributions: Populations separated by geographical barriers.

  • Edaphic Factors: Soil characteristics that affect plant distribution.

Species Distribution/Dispersion Patterns

• Clumped: Individuals are grouped together, often around resources.

• Uniform: Individuals are evenly spaced, usually due to territoriality or competition.

• Random: Individuals are dispersed unpredictably, often where resources are abundant.

Population Dynamics

• Density-Dependent Factors: Factors that become more influential as population size increases (e.g., disease, competition).

• Density-Independent Factors: Factors that affect populations regardless of size (e.g., weather, natural disasters).

• Population Growth:

  • Exponential Growth: J-shaped curve, rapid growth without limits (e.g., bacteria).

  • Logistic Growth: S-shaped curve, includes carrying capacity (K), where growth slows as resources become limited.

• Carrying Capacity: Maximum population size that the environment can support.

Population Structure

• Age/Stage Structure: Distribution of individuals across different ages or life stages.

• Life Cycle Graphs: Show population stages and transitions (e.g., juvenile to adult).

• Annuals, Biennials, Perennials:

  • Annuals: Complete life cycle in one year.

  • Biennials: Complete life cycle in two years.

  • Perennials: Live for multiple years.

• r-Selected vs. K-Selected Species:

  • r-Selected: Fast growth, many offspring, short lifespan (e.g., weeds).

  • K-Selected: Slow growth, fewer offspring, longer lifespan (e.g., elephants).

Community Ecology

• Community Ecology: Studies the interactions between species within a community.

• Interaction Types:

  • Mutualism, Commensalism, Antagonism.

• Plant Mutualisms:

  • Pollination: Plants benefit from pollinators like bees; pollinators get food (nectar).

  • Seed Dispersal: Seed dispersers (e.g., birds) move seeds and benefit from food (fruits).

  • Protection Mutualisms: Plants provide shelter (domatia) or food (extra-floral nectaries) for insects.

  • Root Associations: Mycorrhizal fungi provide nutrients to plants in exchange for carbohydrates.

Antagonisms

• Pathogens: Harmful organisms like fungi (e.g., rusts).

• Parasites: Organisms that live off a host (e.g., mistletoe).

• Herbivores: Animals that feed on plants, causing damage (e.g., grazers, browsers).

• Nectar Robbers: Organisms that steal nectar without pollinating the plant.

Tolerance vs. Resistance

• Tolerance: Ability of a plant to endure adverse conditions (e.g., drought).

  • Compensation: Plant regrows after damage.

  • Overcompensation: Regrowth that exceeds original condition.

• Resistance: Plant ability to prevent or reduce damage.

  • Mechanical Defenses: Thorns, spines (e.g., cacti).

  • Chemical Defenses: Toxins (e.g., alkaloids in tobacco).

  • Indirect Defenses: Attracting predators of herbivores (e.g., plants releasing volatiles to attract ladybugs).

Interspecific Competition

• Niches: The role an organism plays in its ecosystem.

• Competitive Exclusion: One species outcompetes another, leading to local extinction.

• Niche Partitioning: Species divide resources to reduce competition.

Trophic Interactions

• Trophic Levels: The position of organisms in a food chain (producers, consumers).

• Autotrophs vs. Heterotrophs:

  • Autotrophs: Make their own food (e.g., plants).

  • Heterotrophs: Eat other organisms (e.g., herbivores, carnivores).

• Decomposers: Organisms that break down dead matter (e.g., fungi).

• Food Chains and Webs: Show how energy flows through ecosystems.

Tritrophic Interactions

• Bottom-Up Effects: How resources at lower trophic levels affect higher levels.

• Top-Down Effects: How predators affect lower trophic levels.

• Trophic Cascades: Changes in one trophic level affect the whole system.

Plant Community Diversity

• Species Richness: The number of species in a community.

• Relative Abundance: Proportions of each species in a community.

• Shannon Diversity Index: Measures community diversity.

Keystone Species

• Keystone Species: A species that has a disproportionately large effect on its environment (e.g., sea otters).

Succession

• Primary Succession: Development of an ecosystem in an area without soil.

• Secondary Succession: Recovery of an ecosystem after disturbance.

• Pioneer Species: Early colonizers in primary succession.

• Climax Community: A stable and mature community at the end of succession.

Landscape Ecology

• Fragmentation: Breaking of habitats into smaller patches.

• Edge Effects: Changes in ecological conditions at the boundary of habitats.

• Connectivity: How habitats are connected, allowing species movement.

Island Biogeography

• Island Size and Distance: Larger islands and those closer to mainland have more species richness.

Ecosystem Ecology

• Net Primary Productivity: The rate at which plants produce biomass.

• Biogeochemical Cycles: The cycling of elements like carbon, nitrogen, and water.

  • Water Cycle: Evaporation, precipitation, runoff.

  • Nitrogen Cycle: Nitrogen fixation, nitrification, denitrification.

Biomes

• Biomes: Large ecological areas defined by climate, plant growth forms, and species.

  • Tropical Forests: Warm, wet, diverse.

  • Savannas: Grasslands with scattered trees.

  • Deserts: Dry, sparse vegetation.

  • Shrublands: Dense shrubs, semi-arid conditions.

  • Grasslands: Dominated by grasses, few trees.

  • Temperate Deciduous Forests: Four seasons, trees shed leaves.

  • Taiga: Coniferous forests, cold winters.

  • Tundra: Cold, low-growing plants, permafrost.