Ecology: Ecosystems and Classifications

• Ecology is the study of the relationships between organisms and their natural habitat, including interactions with their surroundings
• Oekologie (Ecology) was coined by German biologist Ernst Haeckel in 1866
• The Greek word "Oikos" means "home," and "Logos" means "study"

Autecology and Synecology

• Autecology deals with the study of single species or organisms
• Synecology deals with the study of multiple species or groups of organisms

Ecosystem Basics

• The term "Ecosystem" was first used in 1935 by British ecologist Arthur Tansley
• It is defined as a basic structural and functional unit of ecology
• An ecosystem has a definite structure and role in its specific environment, such as grasslands, forests, and aquatic ecosystems
• Ecosystems are self-regulating groups of biotic communities of species and their non-living environment which exchange energy and matter

Types of Ecosystems

• Natural Ecosystems are categorized by
  • Aquatic Ecosystems including fresh, running, and standing water
  • Marine Ecosystems
  • Terrestrial Ecosystems including grassland, forest, and desert
• Artificial/Engineered Ecosystems exist as well

Ecosystem Structure

• Biotic components in an ecosystem include:
  • Producers (photo-autotrophs, chemo-autotrophs like Nitrosomonas, iron bacteria, methanogens)
  • Consumers (herbivores, carnivores, omnivores, detrivores)
  • Decomposers
• Abiotic components in an ecosystem include:
  • Physical elements like climate, soil type, soil moisture, and geographic elements like latitude, longitude, and altitude
  • Chemical elements like macro/micro nutrients, trace elements, pollutants, and organic substances

Functional Components of Ecosystems

• Includes the food chain, food web, trophic levels, and energy flow
• Biogeochemical cycles are:
  • Gaseous Cycles in which the cycle C, N, O and Hydrological Cycle
  • Sedimentary Cycles in which the cycle Phosporus Cycle and Suplhur Cycle

Food Chains

• It defines the linkage between living organisms (plants/animals) for the transfer of food energy
• Food chains are not simple and straight
• Grazing food chains have their energy flow begins with plants fixing sunlight
• Detritus food chains have their energy flow begin with dead organic matter broken down by decomposers

Food Webs

• Define how different food chains interconnect
• The significance incorporates energy flow, nutrient cycles, ecological balance, and population size regulation
• Food chains sharing a number of steps belong to the same trophic level

Trophic Levels

• This is the various steps in a food chain where the transfer of food or energy takes place
  • Order consists of Producers, Consumers, and Decomposers

Ecological Pyramids

• Illustrate how energy and biomass decrease from lower to higher trophic levels
• The producer or first trophic level makes up the base
• The successive three levels make the apex
• Ecological pyramids can be based on numbers, biomass, or energy

Types of Ecological Pyramids

• Pyramid of Numbers: Illustrates the relationship between herbivores, producers, and carnivores in terms of their numbers
• Pyramid of Biomass: Illustrates the quantitative relationships of standing crops
• Pyramid of Energy: Illustrates the rate at which food is produced and are upright in shape

Energy Flow

• Energy flow in the environment is unidirectional
• An universal energy flow model applies to all living components where:
  • I = Energy input
  • A = assimilated energy
  • P = Production
  • NU = Energy not used
• Models include single channel and Y-shaped energy flow

Nutrient Cycling

• The key elemental cycles which are necessary for life

Homeostasis

• This is the resistance to changes in the external environment
• It's the tendency to maintain a stable and relatively constant internal environment
• It was observed by Claude Bernard in 1865 and named by Walter Bradford Cannon in 1926
• Effector, receptor, and a control center is needed to regulate homeostasis,
• Positive feedback stimulates change to allow rapid changes within ecosystems
• Negative loops are often used to maintain homeostasis

Ecological Succession

• It can be defined as the gradual ecosystems change and develop over time
• It is a series of predictable temporary communities or stages leading up to a climax community
• Each temporary community is a successional stage or seral stage
• Each stage is prepared for the land and the next stage
• All habitats are in a constant state

Types of Succession

• Primary succession happens in new habitats that were never colonized
• Secondary succession happens in previously colonized, disturbed/damaged habitats

Succession Classification by Area

• Hydrarch/Hydrosere happen in ponds, swamps, and bogs
• Mesarch happen in areas with adequate moisture
• Xerarch/Xerosere happen in dry lands
• Lithosere happens on bare rock
• Psammosere happens on sand
• Halosere happens on saline soil

Ecological Succession Process

• Nudation: Bare areas occur due to volcanic eruptions, flooding, landslides, erosion, etc.
• Invasion: Arrival of reproductive bodies or propagules of organisms settling in the bare area
• Competition and Co-action: An increased number of species in a limited space
• Reaction: Changes to land, soil, water, and temperature by living organisms
• Stabilization: Terminal communities stabilize and maintain equilibrium with the climate, forming a climax community such as grassland, forests, or coral reefs

Forest Ecosystems

• Abiotic factors: inorganic/organic substances in soil, temperature, humidity, rainfall, light, and biogenic gases (CO2, O2)
• Biotic factors: large trees, herbs, lianas, orchids as producers; deer, elephants, moles as primary consumers; snakes, lizards as secondary consumers; and tigers, lions as tertiary consumers
• Includes tropical rain forests, tropical deciduous forests, sub-tropical forests, temperate rain forests, temperate deciduous forests, and evergreen coniferous forests

Tropical Rainforests

• These have tropical regions with high rainfall, humidity, and temperatures
• They are rich in biodiversity
• Contain a variety of animals such as: jaguar, tapir, okapi, boa constrictor, African grey parrot, keel-billed toucan, crowned eagle, three-toed sloth, spider monkey, and large flying fox.
• Layers are divided into emergent, canopy, understory, and forest floor levels
• Amazon/Congo rainforests, and Southeast Asian rainforests are examples

Tropical Deciduous Forests

• It forms a natural cover on most parts of India and are split into dry and moist types
• They occur on the eastern coasts of Western Ghats, North eastern parts of Peninsular Chhota Nagpur plateau, and regions along the Shiwaliks.
• The trees shed their leaves periodically, economically important for timber like sal and teak.

Sub-Tropical Forests

• A forest within or bordering the tropical zone that has relatively less variation in temperature
• Subtropical rainforests exist in Central America, the West Indies, India, Madagascar, and mainland Southeast Asia
• Small deciduous trees and shrubs are also common sights

Temperate Rain Forests

• These are located along the Pacific coast of North America, Chile, Norway, the United Kingdom, Japan, Australia, and New Zealand
• Characterized by mild weather, rainfall, coniferous trees, evergreens, and animals which include black bears, lynx, and wolves

Temperate Deciduous Forests

• These forests are located in mid-latitude areas between polar regions and the tropics
• There are extremes in conditions such as color change with loss of leaves, broadleaf trees of oak/maple/beech/hickory/chestnut as well as toads, chipmunks, and gray squirrels

Evergreen Coniferous Forests

• These forests are south of the arctic tundra
• They face winters that are long, cold, and dry with sunlight available for only a few hours
• The soil has less nutrients and is acidic
• There are a variety of animals such as: moose, deer, reindeer, squirrels, wolves, bears, foxes, owls, woodpeckers, and hawks

Grassland Ecosystems

• These ecosystems consist of inorganic elements (C, H, O, N, P, S), alongside temperature, humidity, rainfall, and light
• Biotic compounds have scattered trees, grasses, and grazing animals
• Includes tropical (Savannas), temperate and polar grasslands

Tropical Grasslands

• These areas are near the equator between the tropics of Capricorn and Cancer, which dry but have seasons of heavy rain
• They rely on: grasses, bison, zebra, buffalo, kangaroos, termites, lions, hyenas, elephants

Temperate Grasslands

• Trees/shrubs are uncommon with extreme cold winters (-40°C) and hot summers (38°C) over a gentle slope
• Rodents, bisons, wolves, hawks, and owls live there
• Eexamples include: North America (Pampas), South Africa (Veldts), Europe and Asia (Steppes), as well as Australia (Downs)

Polar Grasslands

• These areas feature strong and severe cold winds with arctic animals
• An example of the region is the Arctic Tundra
• Permafrost maintains as soil, rocks, as well as sediments that is in a frozen state for a span of two years and over

Desert Ecosystems

• About a third of the world's area is covered with the desert
• Tropical deserts are the hottest and driest places on earth with sporadic precipiation
• Tropical deserts' characteristics: Sahara, Kalahari, Thar, Mexican, Great Australian desert
• Temperate deserts are much colder with terrain covered in rocks and pebbles
• Temperate deserts' characteristics: Mojave and Sonoran Deserts
• Cold deserts occur in colder regions with cold summers and exteremely cold winters
• Cold deserts' characteristics: Atacama, Gobi, Great Basin, Namib, Iranian, Takla makan, and Turkestan

Pond Ecosystems

• Ponds are small stagnant freshwater ecosystems that can be seasonal and exposed to anthropogenic activities

Lake Ecosystems

• Aquatic organisms include:
  • Plankton
  • Nektons
  • Neustons
  • Benthos
  • Periphytons
• Lake stratification involves epilimnion (warm, light) and hypolimnion (cold, viscous) layers

Types of Lakes

• Oligotrophic lakes are low in nulcear content
• Eutrophic content
• Dystrophic Lake of lower pH: (Eg: Lake Suchar II in Poland), lakes Allgjuttern, Fiolen and Brunnsjön in Sweden
• Endemic lakes are ancient and deep with endemic fauna
• Desert salt lake: High salt content - Eg: Great Salt Lake in northern Utah, USA
• Volcanic lakes, mermicic lakes (permanently stratified), and artificial lakes

Stream Ecosystems

• There are 3 main phase structures to streams, including:
  • Mountain highland
  • Second phase
  • Third phase

Ocean Ecosystems

• Oceans support diverse life and have an impact on weather conditions and climate
• Flora consists of seaweeds/marine sea grasses/marine algae, and phytoplanktons
• Fauna comprises protozoans, marine invertebrates (echinoderms, mullosks, sea anemones), and marine organisms