Biomes and Origins fo Plants

Biomes

Major communities classified by vegetation and organism adaptations, Climate is a key abiotic factor, Different classification schemes exist.,

Plant-Environment Interaction

Understanding ecosystems requires understanding plant interactions with their environment.,

World Biomes

Different biomes classified based on climate and vegetation.,

Temperate Deciduous Forests

Found in temperate regions with plentiful water, Characterized by deciduous leaves adapted to freezing temperatures.,

Coniferous Forests

Includes Boreal Forest and Taiga, Harsh climate limits productivity.,

Tropical Rain Forests

High rainfall, warm temperatures, Rapid decomposition and nutrient cycling, Sensitive thin soil.,

Tropical Savannahs and Grasslands

Low rainfall prevents forests, Seasonal climates with fires, Deep-rooted hardy plants.,

Tundra

Treeless, Short growing season, Arctic tundra: low productivity, Alpine tundra: intense solar radiation and potential drought.,

Temperate Grasslands

Grass communities with seasonal flowering plants, Few trees due to low rainfall, Thick organic soils.,

Deserts

Low moisture, Unpredictable rainfall, Wide temperature fluctuations, Plants adapted for water conservation.,

Elevation Impact

Changes in elevation cause biome shifts over short distances.,

Aquatic Biomes

Shaped by water temperature, nutrients, currents, salinity, and waves.,

Global Productivity

Ecosystem productivity varies per area unit, Primary productivity combines per-unit productivity with Earth’s surface coverage.,

Origin of Chloroplasts

Chloroplasts have their own DNA, Derived from ancestral cyanobacteria, Endosymbiosis occurred more than once.,

Origin of Oxygen

Early Earth lacked oxygen, Photosynthetic organisms caused Great Oxidation Event, Major atmospheric change.,

Terrestrial Transition Challenges

Drying out: solved by waxy cuticle, Gas exchange: closable stomata, Support: lignin for strength, Transport: roots and vascular tissue, Fertilization: pollen grains.,

Leaf Adaptations

Waxy cuticle, Defensive compounds, UV protection, Stomata for gas exchange.,

Cell Wall Support

Stronger cell walls with cellulose, hemicellulose, and lignin.,

Vascular Tissue

Xylem: water transport from roots to leaves, Phloem: transports photosynthetic products in both directions.,

Reasons for Terrestrial Transition

Originated from freshwater green algae, Pre-existing desiccation resistance, Competition in aquatic habitats pushed adaptation.,

Landfall Traits

Plants and green algae share chlorophyll a & b, Store energy as starch, Cell walls made of cellulose.,

Fossil Evidence

Land plants originated in Mid-Cambrian to Lower Ordovician, Vascular plants in Upper Ordovician, Earliest plant macrofossils from Middle Silurian, Trilete spore microfossils found earlier.