Understanding the Biosphere and Terrestrial Biomes

The Biosphere

• The biosphere is Earth's life zone, located between the lithosphere and troposphere.
• Terrestrial life is organized into biomes, while aquatic life is categorized by freshwater and marine zones.

Terrestrial Biomes

• Biomes are large-scale communities shaped by the physical environment and categorized by dominant vegetation growth forms.

• Biomes show the impact of climate variation and serve to model the impacts of environmental change.

• There are nine main biomes: tropical rainforest, tropical seasonal forest and savanna, desert, temperate grassland, temperate shrubland and woodland, temperate deciduous forest, temperate evergreen forest, boreal forest, and tundra.

• Tropical forests have high diversity, while polar regions have low diversity.

• Biomes are also classified by plant growth forms, leaf characteristics, and succulence.

• Climate mainly determines biome distribution, with temperature and precipitation being most important.

• Climate diagrams show average monthly temperature and precipitation, helping to identify water deficit or subfreezing periods.

Tropical Rainforests

• Located in low-latitude tropics, with high precipitation and warm temperatures year-round and no distinct seasons.
• They contain about 50% of Earth's species, storing about 37% of terrestrial carbon.
• Vertical structure includes: trees, canopy, lianas/epiphytes, understory, forest floor.
• Key threats: deforestation for agriculture and pasture.

Tropical Seasonal Forests and Savannas

• Located adjacent to rainforests, towards Tropics of Cancer and Capricorn.
• Characteristics of these biomes include seasonal rainfall, shorter trees, drought-deciduous trees, and more grasses and shrubs. Frequent vegetation fires.

Deserts

• The location of these biomes is in subtropical regions, with high temperatures and low water availability.
• Adaptations include stem succulence, short life cycles and drought-deciduousness.
• Desertification can result from unsustainable grazing and agriculture.

Temperate Grasslands

• Located in 30° to 50° N and S latitudes, with moist summers and cold winters.
• Characteristics include grass-dominated vegetation maintained by fire and grazing.
• Face threats include agriculture conversion and overgrazing.

Temperate Shrublands and Woodlands

• Climate: Winter rainy season, dry summers.
• Vegetation includes evergreen shrubs and trees with sclerophyllous leaves
• Common fires help maintain diversity within these biomes.
• Face threats including conversion to agriculture, urbanization, increased fire frequency.

Temperate Deciduous Forests

• Deciduous leaves are an adaptation to freezing with sufficient rainfall and fertile soils.
• Location: Primarily Northern Hemisphere
• Species include oak, maple, and beech trees
• Threats come from agriculture

Temperate Evergreen Forests

• Tree adaptations to a wide range of conditions, including warm coastal to cool continental/maritime climates.
• Located between 30°-50° latitude in both hemispheres.
• Experience clear cutting as well as alteration of the ecology through non-native species.

Boreal Forests (Taiga)

• Winters feature subfreezing temps, 6 subfreezing months, and little precipitation with permafrost.
• Located 50°-65°N.
• Threats include logging, oil/gas development.

Tundra

• Tundra is characterized by treeless environment consisting of low-growing shrubs, sedges, forbs, grasses, lichens, and mosses.
• Tundra occurs where there are cold climates and little precipitation with permafrost and long summer days.
• Concerns: Energy resource development impact permafrost.

Mountains

• Elevational bands of biotic communities change with rapid climate.
• Temperatures decrease with elevation.
• High wind speeds, intense solar radiation, and lower atmospheric composition are challenges.

Freshwater Ecosystems

• Freshwater ecosystems connect terrestrial and marine environments, processing as well as transporting chemical elements.
• Biota correlates with physical characteristics of water.

Streams and Rivers

• With smallest streams being 1st order in higher elevations, these converge into other streams downstream.
• Riffles move fast and are oxygen rich while pools run deeper but slower.
• Stream bottom features invertebrates.

Lakes and Ponds

• Nutrient as well as energy status depends on size as small surface areas within lakes are nutrient-poor while the opposite is true for nutrient-rich areas.
• Plankton (phytoplankton and zooplankton) live in open water, inhabited by plankton and fish.
• The nearshore environment of the photic zone is the littoral zone, which is densely populated with macrophytes.

Marine Ecosystems

• Marine biological zones are categorized by salinity, degree of light, and substrate stability.

Nearshore zones

• Estuaries: River-ocean junctions, varying salinity, enriched sediments and nutrients and vital nursery grounds that are threatened by pollution.

• Salt Marshes: Plants dominate with high productivity because of nutrient input with a salinity gradient.

• Mangrove Forests: Location: Tropical/subtropical

• Invertebrates occur beneath the sand on unstable substrates and limited vegetation.

Shallow Ocean Zones

• Coral Reefs: Warm, shallow waters that maintain algae, forming a cooperative relationship
• Seagrass and Kelp Beds: Submerged flowering plants provide food and support diverse communities.

Open Ocean and Deep Benthic Zones

• Light availability dictates the life density within the ocean as light is critical for photosynthesis.
• Below the photic zone is a deep sea that does not receive any light but features bizarre-shaped organisms.

Impacts of Marine Ecosystem

• The ecosystem encounters widespread damage from activities on both land and sea and suffers from greenhouse gas emission resulting in temperature changes and pollution.

Environmental Tolerances

• Each species features a variety of tolerance relating to geographic dispersion.
• Organisms can adjust to stress factors using acclimatization.
• Adaptation to greater elevations entails increases in respiration, construction of red blood cells, and pulmonary blood pressure.

Environmental Variation

Responses to Environmental stress

• Response decreases when subjected to a stress level.
• To combat stress, acclimatization can be implemented.
• Selection in nature breeds individuals best able to work under stress.
• Population undergoes adaptation in line within natural selection.

Thermal Regulation

• Enzyme activity is sensitive to temp because their catalyzing proteins are stable.

• Enzymes are not stable only under a certain range of temps.

• Conduction of energy moves between levels that are cooler and more hot.

• Convection: Moving fluid transports heat.

• Heat absorbs water when transitioning between states.

• Inputs and outputs of energy include IR radiation given off in surroundings.

• Hairs on the surfaces that repel solar energy can reduce conductive heat reduction.

Water and Temperature Variation

• Transpirational cooling is bad, but some plants lose leaves through drought.
• Pubescence includes hairs located on leaf surfaces.
• Convection serves as a method to remove heat within environments rich in minerals.
• Surface hugging occurs to prevent strong convection conditions.
• Insulation that results from hair cuts convective heat reduction.

Temperature Adaptation

• Animals generate heat internally in especially birds and mammals.
• Bodies regulate temperature using outside sources.

Thermoneutral Zone

• Constant resting metabolic rate takes place.
• When heat exits greater than metabolic temperature drops along with rate of metabolic heat generation.

Evaporation

• Includes panting and perspiring.
• Animals existing in tropical temperature have less tolerance than those adapting to artic temps.
• Aquatic environment are divided between hyperosmotic which is high saline, hyposmotic which less saline, and isosmotic which is same concentrations.

Potential Adaptation

• Cells must adjust or stay hydrated.
• Microorganisms protect dry condition.
• Terrestrial microorganisms generally take root.
• Water is taken and put in direction of gradient.

Resisting Water Loss

• Waxy cuticles or skins work against water loss.

Plants and Water Usage

• Plants take in water through roots but older roots have limited consumption.
• Soil-dependent roots that have oxygen are able to stop breathing.

Water Loss

• Plant loss while open because in higher levels there is 100% degree of humidity.

Sources of Energy

• Energy assimilated using sunlight, inorganics acids, for autotrophs and heterotrophs.

Autotrophy

• Chemosynthesis uses energy from inorganic compounds.
• Light harvested and used for split H20, allowing electrons into ATP.
• CO2 is fixed when carbohydrates synthesize.

Photosynthetic Pathways

• Biochemical processes result in effective photosynthesis.
• When light is limited, plants are still damaged, and oxygen decreases while dark reaction occurs with photosynthesis.
• The pathway is also known as crassulacean acid metabolism (CAM).

C3 and C4 Plants

• Stomata in C4 plants open under the night under cold temperatures so little water loss occurs.
• The theory of ideal looking involves animals take into mind time needed for feeding.
• Assumes evolution affects animal energy gain.