Ecology: Levels of Organization

• The study of interactions between organisms and their environment is ecology.
• Ecology is studied at different levels of organizations: species, population, community, ecosystem, biome, and biosphere.

Levels of organization in ecology

• A species consists of organisms that can interbreed to produce fertile offspring.
• At the species level, ecologists study adaptations to the environment.
• A population comprises organisms of the same species living in the same habitat at the same time.
• At the population level, ecologists study environmental factors affecting population size.
• A community includes all populations of different species in the same habitat at the same time.
• At the community level, ecologists study interactions among populations.
• An ecosystem is a unit consisting of a community of organisms and the physical environment.
• Energy flow and material cycling are studied at the ecosystem level.
• A biome comprises a group of ecosystems with similar climate and communities.
• At the biome level, ecologists study how global climate changes affect biomes.
• The biosphere is the highest level of organization and includes all parts of Earth that support life.
• At the biosphere level, the ecological impact of human activities is studied.

Ecosystems

• The ecosystem is the basic functional unit of ecology, composed of biotic (living) and abiotic (non-living) components.
• Biotic components are the community of organisms; abiotic components are the physical environment (soil, water, climate).
• Ecosystems can be small (pond) or large (ocean), but all are self-sustaining, stable, and dynamic.

Organism Interactions

• Organisms in an ecosystem interact by feeding on each other or competing for resources.

Environment

• Organisms interact with their environment, adapting to abiotic factors while also affecting the environment.

Energy Flow

• Energy flows from one organism to another as chemical energy in food as organisms feed on each other.
• Energy cannot be recycled, and eventually leaves the ecosystem as heat.
• Constant energy input is essential to sustain life and maintain ecosystem stability.
• Sunlight is the primary source of energy for most ecosystems, converted into chemical energy by plants through photosynthesis.

Material Cycling

• Unlike energy, materials are cycled between the biotic and abiotic components of an ecosystem.
• The elements that make up today’s organisms have existed since Earth’s formation and are returned to the environment when the organism dies, then reused.

Hong Kong Ecosystems

• Hong Kong possesses diverse ecosystems within its small area.
• Each ecosystem type is defined by its specific environment and the organisms that inhabit it.
• Rocky shores are marine ecosystems with rocks and organisms adapted to withstand strong waves, and resist desiccation.
• Mangroves are intertidal wetland ecosystems in estuaries where freshwater meets the sea; soil is waterlogged with high salt content.
• Freshwater streams have flowing water from upstream to downstream.
• The speed of water flow is a major factor influencing the distribution and abundance of organisms.
• Woodlands in Hong Kong are dominated by broad-leaved trees and support a variety of animals.
• Grasslands are dominated by grasses and herbs. Frequent grazing or fire prevents tree growth.

Aquaponics

• Aquaponics combines aquaculture (raising fish) and hydroponics (growing plants in nutrient solutions) in a symbiotic.
• Fish waste provides nutrients for plants, while plants filter the water, creating a clean environment for fish.
• Microorganisms help break down fish waste into nutrients that plants can absorb.

Importance of Light

• Light intensity affects photosynthesis and plant growth.
• In terrestrial habitats, plants grow tall to avoid being blocked from sunlight, or may have large leaves to absorb light for photosynthesis in shady areas.
• In aquatic habitats, decreases in light intensity affect plant species distribution, with shallow waters plants photosynthesizing the most.
• The relative length of day and night affects plant flowering.

Light's Affect on Activity

• Diurnal animals are active during the day.
• Nocturnal animals are active at night and are adapted to live in dark environments.

Temperature's Affect on Survival

• Temperature affects the distribution of plants and behavior of animals.
• An organism can only survive within a certain temperature range where it is metabolically and structurally adapted.
• Pine trees, wheat, and cabbage tolerate cold regions, while bananas, pineapples, and sugar cane are limited to warm tropical or subtropical regions.

Body Temperature Regulation

• Homoiotherms (mammals and birds) maintain a constant body temperature.
• This allows them to remain active, expanding their geographical range.
• Poikilotherms include fish, amphibians, and reptiles which cannot maintain a constant body temperature.
• Animals in cold climates (penguins, seals) have thick subcutaneous fat, reducing heat loss and acting as an energy reserve.
• Animals in hot climates have larger ears and longer limbs, promoting heat loss via a a larger surface area.

Extreme Temperature Survival

• Animals use behavioral methods: hibernation among amphibians, reptiles, and mammals to reduce metabolic rate.
• Hibernation reduces heat loss during the winter.
• Migrating to warmer regions is used birds and butterflies.

Water Availability

• Rainfall is the main water source for terrestrial organisms.
• Humidity affects the rate of water loss from organisms.

Dry Habitats

• Plants adapted to survive in environments with little water are Xerophytes.
• They have adaptations to conserve water. -Adaptations like extensive root systems, water storage in stems, thick cuticles, leaves modified to spines
• Desert kangaroo rats derive water from metabolism, and have effective kidneys and nasal passages to reduce water loss through concentrated urine and reabsorption from exhaled air.
• They are also nocturnal.

Wind

• Wind affects the distribution and growth of plants. Some plants depend on wind for pollination and seed dispersal.
• Wind direction can affect the direction a plant grows. High winds cause plants to lose significant water through transpiration.
• Special adaptions like fleshy leaves and thick cuticles helps plants in such windy conditions prevent excessive water loss.

Water Currents

• Shore animals protect themselves from strong water currents by having strong shells.
• Barnacles secrete a cement-like substance Chitons and limpets have a muscular foot.
• Crab hide under rocks.

Oxygen Concentration

• Organisms typically need oxygen concentration to survive.
• Terrestrial organisms often rely on water, in addition to, oxygen due to altitude.
• Mangrove plants maximize gas exchange with aerial roots and lenticels.

The Oxygen in water varies

• Temperatures- Soluability of oxygen decreases which in turn effects the concentration of dissolved oxygen decreases
• Water concentration increases the amount the water flows increasing the amount of oxygen.
• Organic Matter- the concentration of desolved oxygen decreases when more material present in Water

Types of Trophic Levels

• Species who need high concentration of oxygen consist of Fast moving waters.
• Species who need low concnetrratoins of dissolved oxygen consist warm , still waters

Soil & composition

• Soil allows a place for roots to grow. Affects plant growth and animals present.
• Size of soil particles is important
• Soil particles in the silt is made of smaller and closely packed soil.
• When floods appear, soil and clay becomes very oxygen low.

Type of Content

• Organic matter comes from nutrients of dead organisms, including animals
• Detritivores and microorganisms decomposes the matter for the organic matter, from humus for better retainiture

Key Point

Soil pH is a measure of the acidity, which improves fertility to plants An abiotic factor affects an organisms in the ecosystem such as light, temp, water avalibililty