Terrestrial and Aquatic Environments: Biomes, Ecosystems, and Species Interactions
Terrestrial Environment
Uneven Conditions and Biome Formation
Climate and weather variations create uneven conditions on Earth, leading to the formation of distinct biomes with characteristic dominant plant communities. Organisms adapt to these communities, influencing the landscape and contributing to biodiversity.
Main Factors of the Physical Environment (Abiotic)
Climate, weather, and soil are key abiotic factors that affect an area’s habitability (ability to support life). Weather refers to short-term atmospheric conditions like temperature, humidity, precipitation, wind, and cloudiness. Climate describes long-term average weather patterns at local, regional, and global scales, often with predictable patterns like seasons in temperate zones.
Causes of Climatic Variation
- Earth’s Tilt: Uneven heating due to Earth’s tilt causes greater temperature and day length variations throughout the year at middle to high latitudes, affecting animal activity.
- Atmospheric Circulation: Heating and rotation of the Earth create variations in precipitation, leading to distinct wet and dry bands. For example, heavy rainfall occurs at the equator, while deserts form in the subtropics.
- Coriolis Effect: Earth’s rotation deflects winds, creating patterns like the northeast and southeast monsoons.
Biomes
Biomes are distinct regions with similar climate, soil, animals, and dominant plants. Examples include tropical rainforests, deserts, grasslands, and tundras. Precipitation and temperature vary significantly across different latitudes, influencing the diversity and distribution of biomes.
Factors of Diversity and Distribution of Biomes
- Soil: Soil is a complex mixture of biotic and abiotic components, including organic matter, minerals, and living organisms. Different soil layers support diverse life forms and influence plant growth.
Ecoregions
Ecoregions are large areas within biomes with distinct communities. They represent a finer scale of ecological classification, reflecting the diversity of ecosystems within broader biomes.
Ecosystems in Singapore
Singapore’s diverse ecosystems include primary and secondary forests, coastal forests, urban forests, reclaimed land, and aquatic and shoreline vegetation like mangroves, beaches, and seagrass meadows.
Aquatic Environment
Hydrologic Cycle
The sun drives the hydrologic cycle, which involves the continuous movement of water between the Earth’s surface and the atmosphere. Precipitation, evaporation, and runoff play crucial roles in this cycle.
Oceans
Oceans are vast and complex ecosystems with varying light, salinity, oxygen, temperature, nutrients, and water movement. Different zones within the ocean support diverse life forms, from the intertidal zone to the deep sea.
Key Factors in Ocean Environments
- Light: Light intensity decreases with depth, creating distinct zones like the epipelagic (sunlit), mesopelagic (twilight), and bathypelagic (midnight) zones.
- Salinity: Salinity varies depending on factors like precipitation and evaporation. The highest salinity levels are found in subtropical regions.
- Oxygen: Oxygen levels depend on photosynthesis and light intensity. The minimum oxygen concentration typically occurs at around 1000 meters depth.
- Temperature: Temperature varies with depth and latitude. The thermocline, a layer of rapid temperature change, separates warmer surface waters from cooler deep waters.
- Nutrients: Nutrients come from primary producers and dead organic matter. Upwellings bring nutrient-rich water to the surface, supporting marine life.
- Water Movement: Wind-driven currents, gyres, and upwellings transport nutrients, oxygen, heat, and organisms throughout the ocean.
Littoral Shores and Tides
The intertidal zone experiences cycles of submergence and exposure due to tides. Different organisms have varying tolerances to air exposure, leading to zonation of species within this zone.
Mangroves and Salt Marshes
Mangroves and salt marshes are important coastal ecosystems found in tropical and temperate regions. They provide habitat for diverse species and play a crucial role in shoreline protection.
Rivers, Streams, and Lakes
Rivers, streams, and lakes are freshwater ecosystems with distinct characteristics. Lakes are classified based on nutrient levels, with eutrophic lakes having high nutrient content and oligotrophic lakes having low nutrient content.
Individuals-Temperature Relations
Adaptation to Microclimates
Organisms adapt to local microclimates through evolutionary processes involving variation, inheritance, selection, and time. These adaptations can be morphological, physiological, behavioral, or related to life history.
Causes of Microclimatic Variation
Microclimates can vary due to factors like elevation, topography, vegetation, and substrate color. For example, vegetation can create shade and affect local temperature and humidity.
Temperature and Performance
Different organisms have optimal temperature ranges for physiological processes like photosynthesis. Plants and animals have evolved various strategies to regulate their body temperature and survive in extreme environments.
Plant Adaptation to Extreme Temperatures
Desert plants have adaptations like reduced leaf size, waxy coatings, and deep roots to minimize water loss and survive in hot, dry conditions.
Temperature Regulation in Animals
Animals regulate their body temperature through physiological and behavioral mechanisms. Endotherms generate their own heat, while ectotherms rely on external sources of heat.
Animals Surviving Extremes
Some animals exhibit temporal heterothermy, adjusting their metabolic rate and body temperature in response to environmental conditions. Hibernation and aestivation are examples of strategies used to survive extreme temperatures.
5 & 6. Populations
Population Distribution
Populations are groups of individuals of the same species within a specific area. Their distribution can be influenced by environmental factors, interactions between individuals, and the structure of the physical environment.
Environmental Limits to Species Distribution
A species’ niche defines the environmental conditions where it can survive, grow, and reproduce. The fundamental niche represents the potential range of conditions, while the realized niche is the actual area occupied by the species, considering factors like competition.
Population Abundance
Population abundance refers to the total number of individuals in an area. Various methods, such as quadrat sampling and mark-recapture, are used to estimate population size.
Applications to Conservation
Understanding population size, distribution, and adaptation is crucial for conservation efforts. The IUCN Red List assesses the extinction risk of species based on quantitative data.
Population Dynamics
Population dynamics involve factors like age distribution, dispersal, and survival patterns. Age distributions can predict long-term viability, while dispersal influences gene flow and population connectivity.
Patterns of Survival
- Type 1: High survival among young, with most individuals dying at old age.
- Type 2: Constant rate of survival throughout life.
- Type 3: High mortality among young, with few individuals surviving to adulthood.
Life History Strategies
- r-selected: Species with high reproductive rates and short lifespans, adapted to unstable environments.
- K-selected: Species with low reproductive rates and long lifespans, adapted to stable environments.
Population Growth Models
- Geometric Growth: Growth occurs in discrete pulses.
- Exponential Growth: Unlimited growth in an ideal environment.
- Logistic Growth: Growth slows and eventually stops as the population approaches carrying capacity.
Impact of Climate Variation
Climate variations, such as El Niño events, can significantly impact population dynamics by affecting food availability and reproductive success.
7 & 8. Species Interactions
Interspecies Competition
Interspecies competition occurs when individuals of different species compete for shared resources, negatively impacting the growth and survival of one or both species.
Ecological Niche
The ecological niche encompasses the total range of conditions where a species can live and replace itself. Gause’s competitive exclusion principle states that two species with identical resource requirements cannot coexist indefinitely.
Resource Partitioning
Resource partitioning is an evolutionary adaptation that allows species to coexist by utilizing different resources or occupying different niches within the same habitat.
Effect of Competition on Niche
Competition can restrict a species’ realized niche in the short term and lead to character displacement, an evolutionary change in traits to minimize competition, in the long term.
Intraspecific Competition
Intraspecific competition occurs between individuals of the same species. It can limit population growth and influence population structure.
Exploitation
Exploitation occurs when one species benefits at the expense of another. Examples include herbivory, predation, parasitism, and disease.
Parasites and Pathogens
Parasites and pathogens can have significant impacts on host populations, influencing their behavior, distribution, and abundance.
Exploitation and Abundance
Exploiters, such as predators and parasites, can regulate prey and host populations, preventing them from exceeding carrying capacity.
Biological Control
Biological control involves using natural enemies, such as predators or parasites, to manage pest populations.
Predator-Prey Relationship
Predator-prey relationships are complex and dynamic, influenced by factors like prey availability, predator efficiency, and environmental conditions.
Refugia
Refugia are areas that provide shelter and protection for prey species, allowing them to persist under predation pressure.
Trophic Cascades
Trophic cascades occur when changes at one trophic level affect multiple levels below it. For example, the presence of predators can influence herbivore populations and plant communities.
Mutualism
Mutualism is a symbiotic relationship where both species benefit. Examples include pollination, seed dispersal, and nutrient exchange between plants and fungi.