Biomes: Terrestrial and Aquatic - Study Notes

Key Concepts and Definitions

• Biome: an area that shares a combination of average yearly temperature and precipitation (climate).

  • Example: camels & cacti have water-preserving traits suited to desert conditions; shrubs & wildflowers store energy in roots to recover quickly after fire in grasslands.

• Nutrient availability shapes which plants can grow in a biome:

  • Tropical rainforest: nutrient-poor soil due to rapid nutrient uptake and heavy rainfall.

  • Boreal forest: nutrient-poor soil due to cold temps and slow decomposition.

  • Temperate forest: nutrient-rich soil due to abundant litter and favorable decomposition.

  • Tundra: low soil nutrients because frozen soils prevent decomposition of dead organic matter.

• Shifting Biomes: as climate changes, biome locations shift (e.g., boreal forests moving north as tundra permafrost melts and lower latitudes warm).

Biome Distribution: Latitude, Altitude, and Climate

• Latitude (distance from equator) determines typical temperature and precipitation patterns, leading to predictable global biome patterns.

• Latitudinal zones:

  • Tundra & Boreal: higher latitudes ($60^\circ$+).

  • Temperate: mid-latitudes ($30^\circ$–$60^\circ$).

  • Tropical: closer to the equator (near $0^\circ$).

• Altitude can mimic latitude: mountains host distinct biomes at different elevations.

• A climograph (Page 7) combines monthly temperature and precipitation:

  • Temperature: line graph

  • Precipitation: bar graph

  • A regional climate profile helps predict which biomes occur where.

The Earth's Major Terrestrial Biomes

• Tropical rainforest

• Tropical seasonal forest / savanna

• Subtropical desert

• Woodland / shrubland

• Temperate grassland / cold desert

• Temperate seasonal forest

• Temperate rainforest

• Boreal forest (taiga)

• Tundra

• Polar ice cap

Deserts: Types and Characteristics

• (Sub)tropical deserts: found at the equator.

• Temperate deserts: found at mid latitudes.

• Cold deserts: found in polar regions.

Desert Adaptations (Plants and Animals)

• Plant adaptations:

  • Shallow root systems or very deep taproots to access water.

  • Large water-storage vesicles.

  • Waxy leaves or reduced leaf surface area; some have leaves absent.

  • Thorns or spines to reduce water loss and deter herbivores.

  • CAM-like water-use strategies: Uptake CO₂ at night to minimize water loss.

• Animal adaptations:

  • Small body size, long limbs, efficient water use.

  • Nocturnal behavior to avoid daytime heat.

  • Burrowing to escape heat and conserve moisture.

• Ecological context:

  • Fragile ecosystems with slow plant growth and slow nutrient recycling.

  • Low species diversity and low water availability limit plant survival.

Grasslands and Savannas

• Clump-forming trees in some savannas; grazing animals common.

• Fire regimes select for fire-adapted species and rapid regrowth.

Tundra and Alpine Environments

• Arctic tundra: permafrost; low nutrients; slow plant growth.

• Alpine tundra: high elevation with cold temps and more sunlight than arctic tundra.

• Plant adaptations: shallow, networked root systems; seeds germinate after fire events.

• Animal adaptations: being fast, grazing specialists, camouflage; long limbs/velocity help in open landscapes.

Forest Biomes: Tropical, Temperate, Boreal

• Tropical (Rainforest):

  • High temperature and moisture.

  • Stratification of niches and rapid nutrient cycling despite poor soils.

  • Nutrients largely stored in the canopy.

• Temperate (Seasonal/Deciduous):

  • Moderate temperature and moisture.

  • Broadleaf trees; rapid decomposition; rich soil.

  • Notable undergrowth diversity in temperate forests.

• Cold (Coniferous/Boreal/Taiga):

  • Evergreen leaves; waxy, needle-like leaves minimize water loss.

  • Nutrient-poor, acidic soils limit undergrowth.

Tropical RF Adaptations (Vegetation & Animals)

• Vegetation:

  • Poor soils; most nutrients stored in tree canopies.

  • Broadleaf evergreen leaves.

  • Extreme diversity of niches; sunlight is a limiting factor.

  • Stratification within canopy supports coexistence.

• Animals:

  • Major pollinators: bees, butterflies, birds, bats.

  • Stratified niches and specialized diets.

Temperate and Boreal Forest Adaptations

• Deciduous Forest Vegetation:

  • Broadleaf deciduous trees.

  • More ground-level diversity and undergrowth; varied habitats for animals.

• Boreal Forest Vegetation:

  • Evergreen leaves; waxy needles.

  • Acidic soils hinder undergrowth.

Mountains: Ecological Roles

• Harbors a majority of the world's forests.

• Home to many endemic species.

• Help regulate Earth's climate and influence sea levels.

• Major storehouses of water; important in hydrologic cycle.

Key Characteristics of Aquatic Biomes

• Depth: influences how much sunlight reaches plants for photosynthesis.

• Temperature: warmer water holds less dissolved O₂, limiting the number of organisms that can be supported.

• Salinity: determines species viability and usage as drinking water (Freshwater vs. estuary vs. ocean).

• Flow: affects which plants/organisms can survive and how much O₂ can dissolve in water.

Freshwater: Rivers & Lakes

• Rivers: high O₂ due to continuous mixing with air; transport nutrient-rich sediments; deltas and floodplains are fertile.

• Lakes: standing bodies of freshwater; important drinking water sources.

  • Littoral zone: shallow water with emergent plants.

  • Limnetic zone: light penetrates; photosynthesis occurs; mainly phytoplankton; no rooted plants.

  • Profundal zone: too deep for sunlight; no photosynthesis.

  • Benthic zone: muddy bottom with invertebrates; nutrient-rich sediments.

Freshwater: Wetlands

• Wetland: soil submerged/saturated for at least part of the year, shallow enough for emergent plants.

• Plants adapted to roots submerged in standing water (e.g., cattails, lily pads, reeds).

• Benefits of wetlands:

  • Stores excess water during storms, reducing floods.

  • Recharges groundwater by absorbing rainfall into soil.

  • Roots filter pollutants from water draining through.

  • High plant productivity due to abundant water and nutrients in sediments.

Wetland Types (Visual Cues)

• Swamp, Marsh, Reeds & cattails, Cyprus tree (wetland components shown in diagrams on the source).

Estuaries and Mangroves

• Estuaries: areas where rivers meet the ocean; mix of fresh and salt water; high productivity due to nutrient-rich sediments deposited by rivers.

• Salt Marshes: coastal estuary habitats in temperate climates; breeding grounds for many fish and shellfish.

• Mangrove Swamps: mangrove trees with stilt roots stabilize shorelines and provide habitat for many species of fish and shellfish; estuary habitats along tropical coasts.

Coral Reefs

• Warm, shallow waters beyond the shoreline; most diverse marine biome on Earth.

• Mutualistic relationship between coral (animals) and algae (plants).

• Coral sequesters CO₂ to build calcium carbonate exoskeletons; algae provide energy to coral via photosynthesis.

• Interdependence: coral cannot survive without algae and algae rely on the habitat and CO₂ from coral.

Intertidal Zones

• Narrow band of coastline between high and low tide.

• Organisms adapt to crashing waves and direct sun exposure during low tide.

• Examples: barnacles, sea stars, crabs that attach to rocks.

• Adaptations like shells and tough outer layers prevent desiccation during low tides.

• Different zones host different species (e.g., spiral wrack secretes mucus to retain water during low tide).

Open Ocean

• Low productivity per unit area; primarily algae and phytoplankton support most life.

• Photic zone: region where sunlight can reach and enable photosynthesis.

• Aphotic zone (abyssal): too deep for sunlight.

• Overall, oceanal photosynthesis and respiration contribute substantially to Earth's O₂ and CO₂ exchange.

Key Concepts and Definitions

• Biome: Area defined by average yearly temperature and precipitation (climate).

  • Example: Camels & cacti adapted to desert; shrubs & wildflowers to grassland fires.

• Nutrient availability influences plant growth:

  • Tropical rainforest: Poor soil (rapid uptake, heavy rain).

  • Boreal forest: Poor soil (cold, slow decomposition).

  • Temperate forest: Rich soil (abundant litter, good decomposition).

  • Tundra: Low soil nutrients (frozen soils, no decomposition).

• Shifting Biomes: Climate change causes biome locations to shift.

Biome Distribution: Latitude, Altitude, and Climate

• Latitude determines temperature, precipitation, and global biome patterns.

• Latitudinal zones:

  • Tundra & Boreal: Higher latitudes ($60^\circ$+).

  • Temperate: Mid-latitudes ($30^\circ$–$60^\circ$).

  • Tropical: Near the equator (near $0^\circ$).

• Altitude mimics latitude: Mountains host diverse biomes at different elevations.

• A climograph (Page 7) shows monthly temperature (line) and precipitation (bar) to predict biome occurrence.

The Earth's Major Terrestrial Biomes

• Tropical rainforest

• Tropical seasonal forest / savanna

• Subtropical desert

• Woodland / shrubland

• Temperate grassland / cold desert

• Temperate seasonal forest

• Temperate rainforest

• Boreal forest (taiga)

• Tundra

• Polar ice cap

Deserts: Types and Characteristics

• (Sub)tropical deserts: Equator.

• Temperate deserts: Mid-latitudes.

• Cold deserts: Polar regions.

Desert Adaptations (Plants and Animals)

• Plant adaptations:

  • Shallow or deep taproots.

  • Large water-storage vesicles.

  • Waxy/reduced/absent leaves; thorns/spines.

  • CAM water-use: CO₂ uptake at night.

• Animal adaptations:

  • Small, long limbs, efficient water use.

  • Nocturnal.

  • Burrowing.

• Ecological context:

  • Fragile ecosystems: slow growth, slow nutrient recycling.

  • Low diversity; low water limits plant survival.

Grasslands and Savannas

• Clump-forming trees in some savannas; common grazing animals.

• Fire regimes select for fire-adapted species and rapid regrowth.

Tundra and Alpine Environments

• Arctic tundra: Permafrost, low nutrients, slow plant growth.

• Alpine tundra: High elevation, cold, more sunlight than arctic tundra.

• Plant adaptations: Shallow, networked roots; seeds germinate after fire.

• Animal adaptations: Fast, grazing specialists, camouflage; long limbs aid movement.

Forest Biomes: Tropical, Temperate, Boreal

• Tropical (Rainforest):

  • High temperature and moisture.

  • Niche stratification, rapid nutrient cycling despite poor soils.

  • Nutrients mainly in canopy.

• Temperate (Seasonal/Deciduous):

  • Moderate temperature and moisture.

  • Broadleaf trees; rapid decomposition; rich soil.

  • Diverse undergrowth.

• Cold (Coniferous/Boreal/Taiga):

  • Evergreen, waxy, needle-like leaves (minimize water loss).

  • Nutrient-poor, acidic soils limit undergrowth.

Tropical RF Adaptations (Vegetation & Animals)

• Vegetation:

  • Poor soils; most nutrients in tree canopies.

  • Broadleaf evergreen leaves.

  • Extreme niche diversity; sunlight is limiting.

  • Canopy stratification supports coexistence.

• Animals:

  • Major pollinators: bees, butterflies, birds, bats.

  • Stratified niches, specialized diets.

Temperate and Boreal Forest Adaptations

• Deciduous Forest Vegetation:

  • Broadleaf deciduous trees.

  • More ground-level diversity and undergrowth; varied animal habitats.

• Boreal Forest Vegetation:

  • Evergreen, waxy needles.

  • Acidic soils hinder undergrowth.

Mountains: Ecological Roles

• Harbors most of the world's forests.

• Home to many endemic species.

• Regulate Earth's climate and influence sea levels.

• Major water storehouses; important in hydrologic cycle.

Key Characteristics of Aquatic Biomes

• Depth: Influences sunlight for photosynthesis.

• Temperature: Warmer water holds less dissolved O₂.

• Salinity: Determines species viability and drinking water use.

• Flow: Affects organism survival and O₂ dissolution.

Freshwater: Rivers & Lakes

• Rivers: High O₂ (mixing with air); transport nutrient-rich sediments; fertile deltas/floodplains.

• Lakes: Standing freshwater, important drinking water sources.

  • Littoral zone: Shallow, emergent plants.

  • Limnetic zone: Light penetrates, photosynthesis; phytoplankton; no rooted plants.

  • Profundal zone: Too deep for sunlight; no photosynthesis.

  • Benthic zone: Muddy bottom, invertebrates; nutrient-rich sediments.

Freshwater: Wetlands

• Wetland: Soil submerged/saturated part of year, shallow enough for emergent plants.

• Plants adapted to submerged roots (e.g., cattails, lily pads, reeds).

• Benefits:

  • Stores excess water during storms, reduces floods.

  • Recharges groundwater by absorbing rainfall.

  • Roots filter pollutants.

  • High plant productivity (water, nutrients).

Wetland Types (Visual Cues)

• Swamp, Marsh, Reeds & cattails, Cyprus tree (visual cues from diagrams).

Estuaries and Mangroves

• Estuaries: Rivers meet ocean; fresh/salt mix; high productivity (river sediments).

• Salt Marshes: Coastal estuary, temperate; breeding grounds for fish/shellfish.

• Mangrove Swamps: Mangrove trees with stilt roots; stabilize shorelines, habitat; tropical coasts.

Coral Reefs

• Warm, shallow waters; most diverse marine biome.

• Mutualism: coral (animals) and algae (plants).

• Coral sequesters CO₂ to build CaCO₃ exoskeletons; algae provide energy via photosynthesis.

• Interdependence: Coral relies on algae, algae on coral habitat/CO₂.

Intertidal Zones

• Narrow coastline band between high/low tide.

• Organisms adapt to crashing waves and sun exposure at low tide.

• Examples: barnacles, sea stars, crabs attached to rocks.

• Adaptations (shells, tough layers) prevent desiccation.

• Different zones host different species (e.g., spiral wrack secretes mucus to retain water).

Open Ocean

• Low productivity per unit area; primary life from algae/phytoplankton.

• Photic zone: Sunlight reaches for photosynthesis.

• Aphotic zone (abyssal): Too deep for sunlight.

• Ocean photosynthesis/respiration significantly contributes to Earth's O₂/CO₂ exchange.