Earth's Life Support Systems and Biodiversity
EARTH'S LIFE SUPPORT SYSTEMS
Earth's Components:
Our planet is made of four connected parts:
Lithosphere: The solid Earth, including the inner (solid) and outer (molten) core, plus the mantle and crust.
Hydrosphere: All the water on Earth, in any form (liquid like oceans, frozen like glaciers, or gaseous like water vapor).
Atmosphere: The thin blanket of gases surrounding Earth (mostly 78% nitrogen and 21% oxygen).
Biosphere (Ecosphere): Where all life exists, including all organisms and their interactions.
Energy Flow & Matter Cycling:
Life on Earth relies on energy from the sun, the continuous movement of important elements (carbon, nitrogen, phosphorus, water), and gravity.
Energy Flow: Energy moves one way through an ecosystem, starting from the sun.
Matter Cycling: Essential nutrients (elements) constantly move and get reused within and between ecosystems through natural processes.
Photosynthesis: Plants and other organisms capture sunlight to make food: . This process stores energy.
Ecosystems: These are living systems that can handle some changes, but only up to a certain point.
Ecological Concepts
Ecology: The scientific study of how living things interact with each other and their surroundings.
Biodiversity: The wide variety of life on Earth, including:
Genetic diversity: The different genes within a single species.
Species diversity: The number of different species in an ecosystem (species richness) and how many individuals of each species there are (species abundance).
Ecological diversity: The many types of ecosystems, habitats, and natural processes.
Ecosystem Organization:
Levels of Life: Life is organized from smallest to largest: Atoms → Molecules → Cells → Organisms → Populations → Communities → Ecosystems → Biosphere.
Population: A group of individuals of the same species living in the same area at the same time.
Community: All the different populations (different species) living and interacting in a particular area.
Population Ecology
Carrying Capacity (K): The largest number of individuals of a species that an environment can support indefinitely without running out of resources.
Resource Limitation: When important resources (like food, water, space) are scarce, they stop a population from growing larger.
Population Characteristics:
Size: The total count of individuals in a population.
Density: How many individuals are in a specific area or volume.
Dispersion: How individuals are spread out in an area (e.g., clustered together, evenly spaced, or randomly positioned).
Distribution: The overall geographic area where a population lives.
Population Demographics: The study of how populations change in number and structure over time, looking at birth rates, death rates, and migration.
Population Dynamics: How populations grow, shrink, or otherwise change their size and structure over time.
Population Growth Models: Math equations that describe how populations increase.
Exponential Growth: Rapid, unchecked growth when resources are unlimited, creating a J-shaped curve.
Logistic Growth: Growth that slows down or stops as the population gets closer to its carrying capacity because resources become limited, creating an S-shaped curve.
Growth Rate: How much a population's size changes over a certain period, often shown as a percentage.
Life Strategies (r/K-selection): Different ways species reproduce and survive, depending on their environment.
Biotic Potential: The maximum number of offspring a population could produce if conditions were perfect.
Density-Independent Growth: Factors that affect population size regardless of how crowded it is (e.g., floods, fires, extreme weather).
Density-Dependent Growth: Factors that have a stronger impact as a population becomes more crowded (e.g., competition for food, spread of disease, predators).
Species Interaction & Community Ecology
Types of Species Interactions:
Competition: When individuals or different species fight for the same limited resources.
Predation: One organism (the predator) hunts, kills, and eats another (the prey).
Herbivory: An animal (herbivore) eats plants.
Symbiosis: A long-term, close relationship between two different species.
Mutualism: Both species benefit from the interaction.
Parasitism: One species (the parasite) benefits by harming the other (the host).
Commensalism: One species benefits, while the other is neither helped nor harmed.
Ecological Niche: The unique role and lifestyle of a species in its environment, including where it lives, what it eats, and how it interacts with others.
Resource Partitioning: When similar species in the same area divide up resources (e.g., eating different things, or eating at different times) to avoid direct competition.
Feeding Relationships (Food Chains/Webs): Diagrams showing how energy moves from producers to various consumers in an ecosystem.
Trophic Levels & Energy Loss:
Energy moves up levels: Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers.
Producers: Organisms (like plants) that make their own food using sunlight (photosynthesis).
Consumers: Organisms that get energy by eating other organisms.
Decomposers: Organisms (like bacteria and fungi) that break down dead material, returning nutrients to the soil.
Energy only flows one way and about 90% is lost as heat at each step (the 10% Rule).
Community Structure and Dynamics:
Keystone Species: A species that has a huge impact on its ecosystem, much greater than its numbers suggest, often by controlling other populations or changing the habitat.
Invasive Species: Non-native species introduced to an ecosystem that cause harm to the economy, environment, or human health.
Engineering Species (Ecosystem Engineers): Organisms that physically change their environment, which affects resources for other species (e.g., beavers building dams).
Succession: The natural process of change in the species living in an ecological community over time (e.g., primary succession on new land, secondary succession after a disturbance).
Evolutionary Concepts
Evolution: The gradual change in the inherited traits of living populations over many generations.
Genetic Drift: Random shifts in the frequency of genes in a population due to chance, especially noticeable in small populations.
Bottleneck Effect: A drastic reduction in population size (due to events like natural disasters), leading to a significant loss of genetic variety.
Founder Effect: When a new population is started by a very small group of individuals, leading to a limited genetic diversity compared to the original larger population.
Mutation: A permanent, random change in a DNA sequence.
Natural Selection: The process where organisms best suited to their environment are more likely to survive and reproduce, passing on their favorable traits.
Artificial Selection: Humans intentionally breed plants and animals to select for desirable traits.
Speciation: The evolutionary process where new biological species develop.
Extinction: When an entire species completely dies out from Earth.
Biogeochemical Cycles (Nutrient Cycles)
Biogeochemical Cycles: The paths that chemical substances take as they move through the living (biotic) and non-living (abiotic) parts of Earth.
Carbon Cycle: Carbon moves between the atmosphere, oceans, land, and living things through processes like photosynthesis and respiration; it's vital for all organic molecules.
Nitrogen fromtheairisconvertedintousableformslike through nitrogen fixation, then to and through nitrification, and finally back to by denitrification; essential for proteins and DNA.
Phosphorus Cycle: This cycle doesn't involve the atmosphere much; phosphorus moves mainly through rocks, soil, water, and organisms; crucial for energy (ATP) and DNA.
Hydrologic Cycle (Water Cycle): The continuous movement of water through Earth's atmosphere, land, and oceans via evaporation, precipitation, and runoff.
Eutrophication: When a body of water gets too many nutrients (especially nitrogen and phosphorus), often from land runoff. This leads to excessive plant growth (like algae blooms) which then die, depleting oxygen and killing animal life.
Terrestrial & Aquatic Ecosystems
Biomes: Large regions defined by their climate and dominant plant life (e.g., tundra, boreal forest, temperate forest, desert).
Aquatic biomes: Water-based environments, including oceans (coastal and open sea) and freshwater (lakes, rivers).
Human Impact
Ecosystem simplification: When humans reduce the complexity of ecosystems, often leading to large areas of single crops (monocultures) and a loss of different species.
Conservation: We need to keep an eye on and protect ecosystems to ensure they remain healthy for life.