Earth as a Living Planet

1. Evolution and Biodiversity

Evolution:

• Key Concepts:

  • Population Genetics: Study of genetic variation within populations and how it changes over time.

  • Hardy-Weinberg Equilibrium: Model predicting genotype frequencies in a population under ideal conditions (no mutation, migration, selection, etc.).

  • Types of Selection:

    • Directional Selection: Favors one extreme phenotype.

    • Stabilizing Selection: Favors intermediate phenotypes.

    • Disruptive Selection: Favors extreme phenotypes at both ends.

• Evidence of Evolution:

  • Fossil Record: Shows progression of life forms from simple to complex.

  • Comparative Anatomy: Homologous structures (similar structures in different species due to common ancestry).

  • Molecular Biology: Genetic similarities between species indicate evolutionary relationships.

Biodiversity:

• Species Diversity:

  • Alpha Diversity: Species richness within a specific area or habitat.

  • Beta Diversity: Variation in species composition between habitats or regions.

  • Gamma Diversity: Overall diversity across a large landscape or region.

• Conservation Status:

  • IUCN Red List: Classification of species based on their risk of extinction (e.g., Least Concern, Endangered, Critically Endangered).

2. Population and Community Ecology

Population Ecology:

• Population Density and Distribution:

  • Random Distribution: Individuals distributed unpredictably.

  • Uniform Distribution: Individuals spaced evenly.

  • Clumped Distribution: Individuals grouped in patches.

• Life History Strategies:

  • r-Selection: High reproductive rates, short lifespans (e.g., insects).

  • K-Selection: Fewer offspring, longer lifespans, high parental investment (e.g., elephants).

Community Ecology:

• Species Interactions:

  • Competition:

    • Intraspecific Competition: Competition within the same species.

    • Interspecific Competition: Competition between different species.

  • Predation:

    • Adaptations: Camouflage, mimicry, defensive mechanisms.

  • Mutualism:

    • Examples: Pollination by bees, nitrogen-fixing bacteria in plant roots.

  • Succession:

    • Primary Succession: Development of an ecosystem in a previously uninhabited area (e.g., volcanic islands).

    • Secondary Succession: Recovery of an ecosystem after a disturbance (e.g., forest regrowth after a fire).

3. Ecosystems

Ecosystem Components:

• Trophic Levels:

  • Primary Producers: Autotrophs (e.g., plants, algae).

  • Primary Consumers: Herbivores (e.g., deer, insects).

  • Secondary Consumers: Carnivores (e.g., wolves, birds).

  • Tertiary Consumers: Apex predators (e.g., lions, sharks).

  • Decomposers: Break down dead organic matter (e.g., fungi, bacteria).

Ecosystem Processes:

• Primary Productivity:

  • Gross Primary Productivity (GPP): Total amount of energy converted by photosynthesis.

  • Net Primary Productivity (NPP): Energy available to consumers after accounting for respiration by producers.

• Nutrient Cycles:

  • Carbon Cycle:

    • Processes: Photosynthesis, respiration, decomposition, combustion.

    • Carbon Pools: Atmosphere, oceans, terrestrial biomass, soil.

  • Nitrogen Cycle:

    • Processes: Nitrogen fixation (by bacteria), nitrification, assimilation, ammonification, denitrification.

  • Water Cycle:

    • Processes: Evaporation, condensation, precipitation, infiltration, runoff.

4. Global Climate and Biomes

Climate:

• Climate Zones:

  • Tropical: High temperatures, high precipitation (e.g., Amazon rainforest).

  • Temperate: Moderate temperatures, seasonal changes (e.g., deciduous forests).

  • Polar: Low temperatures, low precipitation (e.g., Arctic tundra).

Biomes:

• Biome Characteristics:

  • Tropical Rainforest: High biodiversity, multi-layered vegetation, high rainfall.

  • Desert: Extreme temperature fluctuations, low moisture, sparse vegetation.

  • Grassland: Dominated by grasses, moderate rainfall, supports large herbivores.

  • Taiga (Boreal Forest): Cold winters, coniferous trees, low diversity compared to tropical forests.

  • Tundra: Permafrost, short growing seasons, low biodiversity, specialized plants and animals.

5. Global Energy and Matter Cycles

Energy Flow:

• Energy Pyramids:

  • Trophic Pyramid: Shows energy loss at each trophic level, with energy decreasing as you move up the pyramid.

• Efficiency:

  • Energy Transfer Efficiency: Typically around 10% from one trophic level to the next.

Matter Cycles:

• Carbon Cycle:

  • Human Impact: Fossil fuel combustion, deforestation leading to increased atmospheric CO₂.

• Nitrogen Cycle:

  • Human Impact: Fertilizer use, industrial processes leading to nitrogen pollution and eutrophication.

• Water Cycle:

  • Human Impact: Water usage, pollution affecting availability and quality of freshwater.

Biodiversity

Biodiversity:

• Components:

  • Genetic Diversity:

    • Gene Pool: Total collection of genes in a population.

    • Genetic Variation: Variability among individuals in a population.

  • Species Diversity:

    • Endemism: Species that are native to and found only in a specific location.

    • Invasive Species: Non-native species that can disrupt ecosystems and outcompete native species.

  • Ecosystem Diversity:

    • Habitat Diversity: Variety of habitats in an area.

    • Ecological Processes: Interaction between different species and their environment.

Conservation Strategies:

• Protected Areas: Establishing national parks, reserves to safeguard habitats.

• Restoration Ecology: Restoring degraded ecosystems to their original state.

• Sustainable Practices: Implementing practices that do not deplete resources or harm ecosystems (e.g., sustainable agriculture, fishing).

Genetic Diversity

Genetic Diversity:

• Importance:

  • Adaptation: Greater diversity allows populations to adapt to changing environments.

  • Disease Resistance: Higher diversity can reduce the impact of diseases.

• Measurement:

  • Allele Frequency: Proportion of each allele in a population.

  • Heterozygosity: Measure of genetic variation within a population (proportion of individuals with different alleles at a gene locus).

Genetic Drift:

• Small Population Effects:

  • Founder Effect: Reduced genetic variation from a small founding population.

  • Bottleneck Effect: Sharp reduction in population size leading to loss of genetic diversity.

Genetic Variability:

• Sources:

  • Sexual Reproduction: Combines genetic material from two parents.

  • Mutations: New genetic variations arise from random changes in DNA.

Evolution

Natural Selection:

• Examples:

  • Pesticide Resistance: Insects developing resistance to chemicals.

  • Antibiotic Resistance: Bacteria evolving resistance to antibiotics.

Speciation:

• Processes:

  • Allopatric Speciation: Occurs when populations are geographically separated.

  • Sympatric Speciation: Occurs without geographical separation, often through genetic changes like polyploidy.

Adaptive Radiation:

• Definition: Rapid evolution of diversely adapted species from a common ancestor in response to new environments.

• Examples: Darwin's finches on the Galápagos Islands, which evolved different beak sizes and shapes to exploit various food sources.

Nonadaptive Evolutionary Processes

Gene Flow:

• Impact: Can introduce new genetic material and reduce differences between populations, counteracting effects of genetic drift.

Genetic Drift:

• Examples:

  • Red Allele: In a small population, random loss of alleles can lead to the red allele becoming rare or disappearing entirely.

Cheetah Genetic Diversity:

• Genetic Bottleneck: Historical events (e.g., glaciations) drastically reduced population size, resulting in low genetic diversity.

Pace of Evolution

Factors Influencing Evolutionary Rates:

• Generation Time: Shorter generation times can lead to faster evolutionary changes.

• Mutation Rates: Higher mutation rates can increase genetic variation.

• Selection Pressure: Intense selection pressures can accelerate evolutionary changes.

Evolutionary Models:

• Gradualism: Evolution occurs slowly and steadily over time.

• Punctuated Equilibrium: Evolution occurs in rapid bursts followed by long periods of stability.

Fossil Evidence:

• Transitional Fossils: Provide evidence of evolutionary changes between major groups (e.g., Archaeopteryx as a link between reptiles and birds).

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Environmental Conditions

Definition:

• Environmental Conditions: These are specific chemical and physical factors in the environment that impact the survival, growth, and reproduction of organisms.

Terrestrial Systems:

• Solar Radiation:

  • Impact: Affects photosynthesis rates, influencing plant growth and energy availability for ecosystems.

  • Variation: Depends on geographic location (latitude), time of year (seasonal changes), and weather conditions.

• Temperature:

  • Impact: Regulates metabolic rates, enzyme activity, and overall physiological processes.

  • Variation: Changes with latitude (closer to poles are colder) and elevation (higher altitudes are cooler).

• Precipitation:

  • Impact: Provides water necessary for plant growth, affects soil moisture levels, and influences plant and animal habitats.

  • Variation: Can be seasonal or vary with climate zones (e.g., tropical vs. arid).

• Soil Type:

  • Impact: Affects nutrient availability, drainage, and root support for plants.

  • Types: Sandy soils drain quickly but may lack nutrients; clay soils retain nutrients but may have poor drainage.

• Nutrient Availability:

  • Impact: Essential for plant growth; deficiencies can limit productivity.

  • Examples: Nitrogen is critical for protein synthesis; phosphorus is important for energy transfer in cells.

Aquatic Systems:

• Temperature:

  • Impact: Influences solubility of gases (like oxygen), metabolic rates, and reproductive cycles.

  • Variation: Colder water holds more oxygen; temperature stratification occurs with depth.

• Solar Radiation:

  • Impact: Affects primary production in aquatic plants and phytoplankton.

  • Variation: Decreases with depth and turbidity (cloudiness) of the water.

• Oxygen Levels:

  • Impact: Essential for respiration in aquatic animals; low levels can lead to hypoxia (low oxygen) zones.

  • Variation: Affected by temperature, water movement, and biological activity.

• Salinity:

  • Impact: Affects osmoregulation in aquatic organisms; high salinity can limit species to specific regions.

  • Variation: Varies from freshwater to marine environments and can fluctuate with tides and rainfall.

• pH:

  • Impact: Influences nutrient availability and the health of aquatic organisms.

  • Variation: Ranges from acidic (low pH) to basic (high pH); affected by pollution and natural processes.

Adaptations to Extreme Conditions:

• Microbes:

  • Examples: Thermophiles thrive in high-temperature environments like hot springs; extremophiles survive in extreme acidity or salinity.

• Plants:

  • Examples:

    • Baobab Tree: Stores water in its trunk and drops leaves to minimize water loss during dry periods.

    • Cacti: Have thick, fleshy stems to store water and reduce water loss.

• Animals:

  • Examples:

    • Polar Bears: Have thick fur and fat layers to insulate against cold.

    • Camels: Can go for long periods without water and tolerate body temperature fluctuations.

Range of Tolerance:

• Concept: Each species has a range of environmental conditions within which it can survive and reproduce.

• Optimal Conditions:

  • Definition: Conditions where species show maximum growth and reproductive rates.

  • Example: Corn thrives in warm temperatures and ample sunlight.

• Less Optimal Conditions:

  • Definition: Conditions where growth may be restricted, and reproduction may be limited.

  • Example: Wheat may survive but not thrive in excessively high temperatures.

• Extreme Conditions:

  • Definition: Conditions beyond which survival is not possible.

  • Example: Marine species exposed to rapid changes in salinity or temperature may not survive.

Measurement of Environmental Conditions:

• Evapotranspiration:

  • Definition: The sum of evaporation from soil and water bodies and transpiration from plants.

  • Calculation: Measured using weather data (temperature, humidity, wind speed) and soil moisture levels.

Resources

Definition:

• Resources: Elements of the environment that are consumed by organisms, such as food, water, light, and oxygen.

Resource Use:

• Consumption: Resources are depleted as they are used; thus, their availability can directly impact the growth and survival of organisms.

Importance at Various Levels:

• Individual Level:

  • Requirement: Adequate resources are necessary for growth, reproduction, and survival.

  • Example: A lion needs sufficient prey to sustain its energy needs.

• Population Level:

  • Requirement: Sufficient resources are needed to support population size and prevent decline.

  • Example: Overfishing can lead to a decline in fish populations due to resource depletion.

• Community Level:

  • Requirement: Diverse species require a range of resources to coexist and maintain ecosystem stability.

  • Example: Coral reefs support a wide variety of species due to the rich resources available.

Resource Availability and Species Diversity:

• Correlation: High resource availability does not always equate to high species diversity due to competition and specialized adaptations.

Example - Salt Marshes:

• Characteristics:

  • High Biomass Production: High primary productivity supports diverse aquatic life.

  • Low Plant Diversity: Dominated by a few plant species adapted to fluctuating salinity and oxygen levels.

• Abiotic Conditions:

  • Salt Concentration:

    • High Salt: During low tide or dry periods due to evaporation.

    • Low Salt: During flooding or heavy rain.

  • Oxygen Levels:

    • Low Oxygen: Due to high microbial decomposition.

    • Adaptations: Plants have air chambers in roots for oxygen exchange.

• Adaptations:

  • Salt Excretion: Specialized tissues in plants excrete excess salt.

  • Air Chambers: Enable plants to survive low-oxygen conditions.

Population Ecology

Definition:

• Population Ecology: Study of how populations of organisms interact with their environment and with each other, and the factors that affect their abundance and distribution.

Factors Affecting Population Size:

• Small Population Size:

  • Genetic Diversity: Lower genetic variation can reduce adaptability and increase vulnerability to diseases.

  • Risk of Extinction: Smaller populations are more susceptible to environmental stochasticity (random changes).

• Large Populations:

  • Survival and Adaptation: Higher genetic diversity increases resilience to environmental changes and stresses.

Aspects of Population Ecology:

• Interactions with Abiotic Factors: How environmental conditions such as temperature and resources affect population dynamics.

• Intraspecific Interactions: Interactions within the same species, such as competition for resources.

• Interspecific Interactions: Interactions between different species, such as predation, competition, and mutualism.

Population Regulation Factors:

• Density-Dependent Factors:

  • Definition: Factors that have a greater impact on populations as density increases.

  • Examples:

    • Competition: Limited resources lead to competition for food and space.

    • Disease: Higher densities increase the likelihood of disease spread.

• Density-Independent Factors:

  • Definition: Factors that affect populations regardless of density.

  • Examples:

    • Weather Events: Extreme temperatures or storms impact populations similarly regardless of size.

    • Natural Disasters: Earthquakes, volcanic eruptions, etc., affect populations indiscriminately.

Density-Dependent Growth (Gause’s Experiment):

• Experiment Details:

  • Setup: Paramecia in a controlled environment with constant food supply and optimal conditions.

  • Findings:

    • Logistic Growth: Population growth initially rapid, slows as resources are consumed and space is limited.

    • Carrying Capacity: Maximum number of individuals the environment can support.

Logistic Growth Model:

• Key Features:

  • Stable Age Distribution: Age ratios remain constant, assuming the population has a consistent birth and death rate.

  • Linear Relationship: Growth rate decreases linearly with increasing density.

  • No Time Lags: Assumes immediate response to changes in density, though real populations may experience delays.

Limitations of the Logistic Model:

• Real-World Deviations:

  • Non-Logistic Growth: Some species show irregular growth patterns due to additional factors like predation or climate variability.

  • Example: Whooping cranes exhibit cyclical population changes due to varying predation pressures.

Applications of the Logistic Model:

• Usage: Provides a framework for managing and predicting population dynamics in both natural and managed environments.

• Challenges: Must account for deviations and additional variables affecting real-world populations.

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Mutualism

Definition and Concept:

• Mutualism: A type of symbiotic interaction where both species involved benefit from the relationship. The benefits can be in terms of increased survival, reproduction, or both.

• Reciprocal Exploitation: The term "mutualism" can be misleading, as it might suggest a purely cooperative interaction. Ecologists view it as "reciprocal exploitation," meaning each species uses the other for its own gain. This implies that if the benefits to one party decrease too much, the relationship may collapse.

Types of Mutualism:

1. Pollination Mutualism:

   • Description: Involves plants and animals (typically insects or birds) that facilitate plant reproduction. Plants offer nectar or pollen as rewards, while animals help with the transfer of pollen from one flower to another.

   • Generalized Pollination:

     • Example: Some pollinators like bees or butterflies visit multiple plant species. This results in a weak, generalized mutualistic relationship because the interaction is not exclusive to any single plant-pollinator pair.

   • Specialized Pollination:

     • Example: Fig trees and fig wasps. Each fig tree species is pollinated by a specific fig wasp species. This is a highly specialized mutualism where the interaction is critical for the reproduction of both species.

2. Resource Partitioning and Evolution:

   • Description: Over evolutionary time, species may adapt to exploit specific resources in a way that reduces competition. This leads to highly specialized mutualistic relationships, as seen in certain plant-pollinator interactions where each partner is uniquely adapted to the other.

Implications:

• Weak Mutualism: When multiple species are involved in the mutualistic network, the interaction between any two specific species is weaker because many alternative interactions exist.

• Specialized Mutualism: When the relationship is highly specialized, it becomes more crucial for the survival of both species involved.

Ecological Communities

Definition:

• Community: A community is an assembly of different populations of species interacting in a specific area. Community ecology focuses on understanding these interactions and how they shape the structure and function of the community.

Food Webs:

1. Concept:

   • Food Web: A food web is a complex network of feeding relationships between different species in a community. It shows how energy flows through the ecosystem from producers to consumers.

2. Components:

   • Primary Producers: Organisms like phytoplankton and multicellular algae that produce energy through photosynthesis.

   • Primary Consumers: Herbivores that feed on primary producers, such as zooplankton that consume phytoplankton and herbivorous fish that eat algae.

   • Secondary Consumers: Carnivores that prey on primary consumers, including carnivorous fish that eat zooplankton and herbivorous fish.

   • Tertiary Consumers: Top predators like tarpons and certain bird species that feed on secondary consumers.

3. Complexity and Dynamics:

   • Complexity: Food webs are more complex than simple food chains because they include all species within an ecosystem and their interconnections.

   • Stability: The removal of a species can disrupt energy flow, but communities often adapt through shifts in species interactions and energy pathways.

Keystone Species

Definition and Importance:

• Keystone Species: Species whose impact on their ecosystem is disproportionately large relative to their abundance or biomass. They play a crucial role in maintaining the structure and health of the community.

Types of Keystone Species:

1. Predator Keystone Species:

   • Example: The sea star (Pisaster) in a Pacific intertidal zone. It preys on mussels and other herbivorous species. Its removal led to mussel overgrowth and the decline of other species, showing its critical role in maintaining balance.

2. Food Source Keystone Species:

   • Example: In tropical forests, figs and nectar serve as crucial food sources during periods of scarcity. Their presence is vital for herbivores during the low-production phases of other plant species.

3. Habitat Modifier Keystone Species:

   • Example: North American beavers, which build dams that create wetlands and ponds. These modifications provide new habitats for various species, demonstrating their role as "ecosystem engineers."

4. Mutualistic Keystone Species:

   • Example: Mycorrhizal fungi that form symbiotic relationships with tree roots. These fungi enhance nutrient uptake for trees, which in turn support a diverse community of forest organisms.

Impact of Loss or Introduction:

• Loss of Keystone Species: Can lead to significant disruptions, such as cascading effects where the absence of one species causes the decline or extinction of others.

• Introduction of Exotic Species: Exotic species can sometimes fill the role of a keystone species, but they can also disrupt existing balance, leading to unpredictable ecological consequences.

Succession

Definition:

• Succession: The gradual process of change and development in an ecosystem over time, characterized by the replacement of species and alterations in community structure.

Types of Succession:

1. Primary Succession:

   • Description: Occurs on surfaces that have never supported life before, such as newly exposed rock surfaces after a volcanic eruption or glacier retreat.

   • Stages:

     • Pioneer Species: Lichens and mosses colonize bare rock, beginning the process of soil formation.

     • Soil Formation: As pioneer species die, they contribute organic matter, creating soil that allows other plants to grow.

     • Intermediate Species: Small plants and shrubs follow, further enriching the soil.

     • Climax Community: Eventually, a stable and diverse community of trees and other plants develops.

2. Secondary Succession:

   • Description: Occurs in areas where the soil remains after a disturbance, such as after a forest fire, hurricane, or human activity.

   • Stages:

     • Initial Colonizers: Fast-growing herbaceous plants and grasses take advantage of the nutrient-rich soil.

     • Intermediate Species: Shrubs and small trees establish, leading to further changes in soil and habitat.

     • Mature Community: A more complex and stable community of trees and diverse plant and animal species forms over time.

Climax Community:

• Concept: Previously seen as the final, stable stage of succession. Modern understanding recognizes that disturbances (fire, wind, pests) continually affect ecosystems, making the climax community a temporary and dynamic state rather than a final endpoint.

Implications:

• Dynamic Nature: Succession is an ongoing process, reflecting the continuous changes and adaptations within ecosystems. Even without disturbances, communities evolve as species interactions and environmental conditions change.

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Terrestrial Biomes

1. Tropical Rainforest

• Location: Equatorial regions such as the Amazon Basin in South America, the Congo Basin in Africa, and parts of Southeast Asia.

• Climate:

  • Temperature: Consistently high, typically between 20°C and 25°C (68°F and 77°F) year-round.

  • Rainfall: Very high, often exceeding 2000 mm (79 inches) annually, with rain distributed evenly throughout the year.

  • Humidity: Often exceeds 80%, contributing to high evaporation and transpiration rates.

• Vegetation:

  • Layers: Emergent layer (tallest trees), canopy (dense upper layer), understory (middle layer), and forest floor (lowest layer).

  • Tree Species: Includes mahogany, rubber trees, and a variety of palms.

  • Epiphytes: Plants like orchids and bromeliads that grow on other plants to access light.

• Biodiversity:

  • Animals: Home to more than half of the world’s plant and animal species; includes jaguars, sloths, a vast array of insects, birds, and amphibians.

  • Interactions: High levels of mutualism (e.g., pollinators and flowering plants), competition, and predation.

• Soil:

  • Characteristics: Generally acidic and low in nutrients because rapid decomposition and uptake by plants prevent accumulation of organic matter.

  • Nutrient Cycling: Fast; most nutrients are stored in the biomass of living organisms rather than in the soil.

2. Tropical Dry (Seasonal) Forest

• Location: Found in parts of Africa, South America, India, and Australia.

• Climate:

  • Temperature: Warm to hot year-round, similar to tropical rainforests.

  • Rainfall: Pronounced wet and dry seasons; annual precipitation ranges from 500 mm to 1500 mm (20 to 60 inches), with a long dry season.

• Vegetation:

  • Adaptations: Deciduous trees that shed leaves to conserve water; trees and shrubs with deep roots.

  • Species: Includes species like the Baobab tree and various drought-resistant shrubs.

• Biodiversity:

  • Animals: Includes herbivores like elephants, and predators such as lions and tigers in some regions; fewer species compared to rainforests.

  • Adaptations: Animals often migrate or enter torpor during dry periods.

• Soil:

  • Characteristics: Less fertile compared to rainforests, but still supports a range of vegetation adapted to seasonal changes.

3. Temperate Rainforest

• Location: Coastal regions of North America (Pacific Northwest), southern Chile, and parts of Australia.

• Climate:

  • Temperature: Mild temperatures ranging from 5°C to 20°C (41°F to 68°F) with minimal seasonal variation.

  • Rainfall: High, often exceeding 2000 mm (79 inches) annually, with rain occurring year-round.

• Vegetation:

  • Dominant Trees: Includes Douglas fir, Sitka spruce, and Western red cedar.

  • Understory: Includes ferns, mosses, and lichens, which thrive in the moist environment.

• Biodiversity:

  • Animals: Includes black bears, cougars, and a variety of bird species.

  • Interactions: High rates of decomposition due to constant moisture, leading to rich soil.

• Soil:

  • Characteristics: Rich in organic matter due to the accumulation of decomposed plant material.

4. Temperate Broadleaf Forest

• Location: Eastern U.S., Europe, East Asia, parts of New Zealand.

• Climate:

  • Temperature: Experiences all four seasons, with warm summers and cold winters.

  • Rainfall: Moderate, ranging from 750 mm to 1500 mm (30 to 60 inches) annually.

• Vegetation:

  • Dominant Trees: Includes oak, maple, and beech.

  • Seasonal Changes: Trees lose their leaves in fall to conserve energy during the winter.

• Biodiversity:

  • Animals: Includes deer, foxes, bears, and a variety of bird species.

  • Adaptations: Animals may hibernate or migrate to cope with seasonal changes.

• Soil:

  • Characteristics: Rich in organic material due to the decomposition of fallen leaves.

5. Boreal Coniferous Forest (Taiga)

• Location: Across northern Canada, Alaska, Russia, and Scandinavia.

• Climate:

  • Temperature: Extremely cold winters and short, mild summers.

  • Rainfall: Moderate, generally between 300 mm and 850 mm (12 to 33 inches) annually.

• Vegetation:

  • Dominant Trees: Spruces, firs, and pines.

  • Adaptations: Trees have needle-like leaves that reduce water loss and withstand snow loads.

• Biodiversity:

  • Animals: Includes moose, lynxes, and various migratory bird species.

  • Adaptations: Animals have adaptations to survive harsh winters, such as thick fur and fat reserves.

• Soil:

  • Characteristics: Generally acidic with low fertility; slow decomposition due to cold temperatures.

6. Temperate Grassland

• Location: North American prairies, South American pampas, Eurasian steppes.

• Climate:

  • Temperature: Warm to hot summers and cold winters.

  • Rainfall: Moderate to low, ranging from 500 mm to 900 mm (20 to 35 inches) annually.

• Vegetation:

  • Dominant Plants: Grasses such as bluestem and buffalo grass; few trees due to limited moisture.

  • Adaptations: Plants have deep root systems to access water and endure drought conditions.

• Biodiversity:

  • Animals: Includes bison, prairie dogs, and various bird species.

  • Adaptations: Animals are adapted to move over large areas in search of food and water.

• Soil:

  • Characteristics: Fertile, rich in organic material due to the decomposition of grasses; supports high agricultural productivity.

7. Tropical Scrub Forest and Savanna

• Location: Africa, parts of Australia, South America.

• Climate:

  • Temperature: Warm year-round.

  • Rainfall: Seasonal, ranging from 500 mm to 1000 mm (20 to 40 inches) annually; dry periods can last several months.

• Vegetation:

  • Types: Grasses with scattered trees and shrubs; vegetation is adapted to survive dry conditions.

  • Adaptations: Trees often have deep roots or drought-resistant features.

• Biodiversity:

  • Animals: Includes large herbivores like giraffes and elephants, and predators such as lions and hyenas.

  • Adaptations: Many animals migrate or have seasonal behavioral changes to cope with dry periods.

• Soil:

  • Characteristics: Generally nutrient-poor; can be prone to erosion if vegetation is removed.

8. Mediterranean

• Location: Mediterranean Basin, parts of California, Chile, and South Africa.

• Climate:

  • Temperature: Mild, wet winters and hot, dry summers.

  • Rainfall: Limited to winter months, typically less than 800 mm (31 inches) annually.

• Vegetation:

  • Types: Dense shrubs, small trees, and aromatic herbs such as rosemary and thyme.

  • Adaptations: Plants have waxy leaves to reduce water loss and fire-resistant traits.

• Biodiversity:

  • Animals: Includes species adapted to arid conditions, such as various lizards and rodents.

  • Interactions: Species have adapted to frequent fires and seasonal changes.

• Soil:

  • Characteristics: Often rocky and nutrient-poor; prone to erosion.

9. Desert

• Location: Includes the Sahara, Mojave, Atacama, and Gobi deserts.

• Climate:

  • Temperature: Can vary widely; hot deserts have extreme temperature fluctuations between day and night.

  • Rainfall: Extremely low, less than 25 cm (10 inches) annually; some deserts experience years with no measurable precipitation.

• Vegetation:

  • Types: Sparse vegetation; cacti, xerophyte shrubs, and hardy grasses.

  • Adaptations: Plants often have water storage capabilities and are adapted to conserve moisture.

• Biodiversity:

  • Animals: Includes camels, lizards, and various nocturnal species adapted to extreme dryness.

  • Adaptations: Many animals have developed nocturnal lifestyles or other adaptations to reduce water loss.

• Soil:

  • Characteristics: Sandy or rocky with low fertility; erosion is common.

10. Tundra

• Location: Arctic regions of the Northern Hemisphere and high mountain areas.

• Climate:

  • Temperature: Extremely cold; short, cool summers and long, harsh winters.

  • Rainfall: Low, generally less than 250 mm (10 inches) annually, mostly as snow.

• Vegetation:

  • Types: Low-growing plants like mosses, lichens, and grasses; few trees due to permafrost.

  • Adaptations: Plants have adaptations to survive in a frozen environment, such as low growth forms and specialized reproductive strategies.

• Biodiversity:

  • Animals: Includes polar bears, Arctic foxes, and migratory birds; populations fluctuate with resource availability.

  • Adaptations: Animals have adaptations to survive extreme cold, including thick fur and fat layers.

• Soil:

  • Characteristics: Permafrost prevents deep rooting; soil is generally low in nutrients and organic matter.

Aquatic Systems

1. Freshwater Systems

• Flowing Waters (Rivers and Streams):

  • Flow: Water continuously moves from source to mouth, influencing sediment and nutrient distribution.

  • Communities: Benthic (bottom-dwelling) organisms include mayflies and stoneflies; fish species adapted to different flow conditions.

  • Water Chemistry: Typically low in salt; oxygen levels can vary with flow rate and temperature.

• Standing Waters (Lakes and Ponds):

  • Stratification: Lakes often have distinct thermal layers (epilimnion, metalimnion, hypolimnion) that affect nutrient distribution and species.

  • Benthic and Open-Water Communities: Benthic zone hosts decomposers and detritivores; open-water zone (pelagic) supports phytoplankton and zooplankton.

  • Eutrophication: Nutrient enrichment can lead to algal blooms and hypoxia (low oxygen), impacting aquatic life.

2. Marine Systems

• Intertidal Zone:

  • Location: Area between high and low tide marks along coastlines.

  • Characteristics: Subject to daily changes in salinity, temperature, and exposure.

  • Species: Includes barnacles, sea anemones, and intertidal fish adapted to variable conditions.

• Pelagic Zone:

  • Zones: Divided into neritic (nearshore) and oceanic (open ocean) zones.

  • Productivity: Highest in neritic zones due to nutrient upwellings; lower in oceanic zones.

  • Species: Includes a wide range of fish, marine mammals, and invertebrates.

• Abyssal Zone:

  • Location: Deep ocean floor beyond 2000 meters.

  • Characteristics: Dark, cold, and high pressure; limited food supply.

  • Species: Includes deep-sea fish, bioluminescent organisms, and unique species adapted to extreme conditions.

3. Wetlands

• Marine Wetlands:

  • Intertidal Zones: Include mangroves and salt marshes.

  • Characteristics: High productivity; important for coastal protection and biodiversity.

• Estuarine Wetlands:

  • Location: Where freshwater from rivers meets and mixes with saltwater from the sea.

  • Characteristics: Highly productive; serves as breeding grounds for many species.

  • Species: Includes various fish, birds, and invertebrates that rely on brackish waters.

• Freshwater Wetlands:

  • Types:

    • Bogs: Peat-forming, acidic, low in nutrients.

    • Marshes: Dominated by herbaceous plants; high productivity.

    • Swamps: Woody plants; often support diverse wildlife.

    • Peatlands: Accumulate peat; important carbon sinks.

  • Importance: Act as water purifiers, flood regulators, and habitats for wildlife.

Hydrologic Cycle

• Components:

  • Precipitation (PRECIP): Includes rain, snow, sleet, and hail that falls from clouds to the Earth’s surface. It can fall directly into bodies of water, onto land, or into vegetation.

  • Evapotranspiration (ET): The combined process of evaporation (water turning into vapor from surfaces like lakes, rivers, and soil) and transpiration (water vapor released from plant leaves).

  • Infiltration (I): The process by which water on the ground surface enters the soil. This water can then move through the soil to replenish groundwater supplies.

  • Runoff (RO): Water, usually from precipitation, that flows over the ground and returns to bodies of water like rivers, lakes, and oceans.

• Pools and Fluxes:

  • Oceans: The largest water pool, holding about 97% of Earth’s water. Evaporation from oceans is the primary source of atmospheric moisture.

  • Terrestrial Water: Includes water in rivers, lakes, glaciers, and soil. It represents a smaller but crucial part of the water cycle.

  • Atmosphere: Contains a small amount of water, but it cycles quickly through precipitation and evaporation.

• Mean Residence Time (MRT):

  • Oceans: Water remains in the ocean for approximately 2,650 years before it is cycled out through evaporation and precipitation.

  • Terrestrial Water: Water stays in terrestrial systems for about 403 years.

  • Atmosphere: Water vapor has a very short residence time of about 8 days before it condenses and precipitates out.

Carbon Cycle

• Processes:

  • Photosynthesis: Plants and phytoplankton absorb CO₂ from the atmosphere and oceans, using sunlight to convert it into organic compounds (sugars) and releasing oxygen.

  • Respiration: Both plants and animals release CO₂ back into the atmosphere as they break down organic matter for energy.

  • Decomposition: Microorganisms break down dead plants and animals, returning carbon to the soil and atmosphere.

  • Combustion: The burning of fossil fuels (coal, oil, natural gas) and biomass (wood, crop residues) releases stored carbon back into the atmosphere as CO₂.

• Pools:

  • Sedimentary Rocks: Carbon is stored in limestone and other sedimentary rocks, representing the largest pool. Carbon here is relatively stable and cycles slowly.

  • Oceans: The ocean stores carbon in dissolved form and as part of marine life. While there is slow exchange with the atmosphere, increased CO₂ levels are causing ocean acidification.

  • Atmosphere: Contains CO₂ and other greenhouse gases. Human activities, such as burning fossil fuels and deforestation, increase atmospheric CO₂ levels.

• Human Impact:

  • Fossil Fuels: The burning of fossil fuels releases ancient carbon, contributing to the greenhouse effect and global warming.

  • Deforestation: Slash-and-burn agriculture and logging reduce carbon sequestration by trees and release stored carbon.

Nitrogen Cycle

• Processes:

  • Nitrogen Fixation: Atmospheric N₂ is converted to ammonia (NH₄⁺) by nitrogen-fixing bacteria in soil or symbiotically with plants (e.g., legumes). Lightning and industrial processes also fix nitrogen.

  • Ammonification: Decomposition of organic matter by microorganisms produces ammonium (NH₄⁺).

  • Nitrification: Ammonium is oxidized first to nitrite (NO₂⁻) and then to nitrate (NO₃⁻) by nitrifying bacteria. Nitrate is a form that plants can readily absorb.

  • Denitrification: Nitrate is converted back to N₂ or N₂O by denitrifying bacteria, releasing nitrogen gas into the atmosphere.

• Pools:

  • Atmosphere: Nitrogen is abundant in the atmosphere but mostly in the form of N₂, which is not directly usable by most organisms.

  • Soil: Contains various forms of nitrogen, including ammonium and nitrate, which are used by plants.

  • Biomass: Nitrogen is a key component of proteins and nucleic acids in living organisms.

• Human Impact:

  • Agriculture: The use of synthetic fertilizers increases nitrate levels in the soil, leading to runoff into water bodies and eutrophication.

  • Pollution: Combustion of fossil fuels releases nitrogen oxides (NOx), which contribute to air pollution and acid rain.

Biodiversity and Ecology

• Biodiversity:

  • Instrumental Value: Includes benefits such as ecosystem services (pollination, water purification) and resources (food, medicine).

  • Intrinsic Value: The inherent worth of species and ecosystems, independent of their utility to humans.

• Genetic Diversity:

  • Within Individuals: Variability in genetic traits among individual organisms.

  • Among Individuals: Variation in genetic traits within a population.

  • Among Populations: Differences in genetic traits among different populations of a species.

  • Among Species: The variety of genetic material among different species.

• Evolution:

  • Natural Selection: Process where organisms with favorable traits survive and reproduce, passing those traits to the next generation.

  • Gene Flow: Movement of genes between populations through migration.

  • Genetic Drift: Random changes in gene frequencies in a population, particularly in small populations.

• Extinction:

  • Mass Extinctions: Large-scale events where a significant number of species go extinct in a relatively short period.

  • Human Impact: Habitat destruction, pollution, and climate change accelerate extinction rates.

• Population and Community Ecology:

  • Population Ecology: Examines factors influencing population size and distribution, including birth rates, death rates, and migration.

  • Community Ecology: Studies interactions among species and their effects on community structure.

  • Succession: The process by which the species composition of a community changes over time, often following a disturbance.

Ecosystems and Global Cycles

• Ecosystems:

  • Components: Interactions between biotic factors (organisms) and abiotic factors (climate, soil, water).

  • Types: Include terrestrial ecosystems (forests, grasslands) and aquatic ecosystems (freshwater, marine).

• Global Cycles:

  • Hydrologic Cycle: The continuous movement of water within the Earth and atmosphere, driven by solar energy.

  • Carbon Cycle: The flow of carbon through the atmosphere, oceans, and living organisms, crucial for regulating Earth’s climate.

  • Nitrogen Cycle: The cycling of nitrogen through the atmosphere, soil, and living organisms, essential for protein synthesis and ecosystem productivity.