BY: Ayushi – MukherjeeCLASS: XI A

What is ecology?

. Ecology is the scientific analysis and study of interactions among organisms and their environment. It is an interdisciplinary field that includes biology and Earth science. Ecology includes the study of interactionsorganisms have with each other, other organisms, and with abiotic components of their environment. Topics of interest to ecologists include the diversity, distribution, amount , and number of particular organisms; as well as cooperation and competition between organisms, both within and among ecosystems. Ecosystems are composed of dynamically interacting parts including organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis, nutrient cycling, and various niche construction activities, regulate the flux of energy and matter through an environment.

ENVIROMENT

• The biophysical environment is the biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development and evolution. The biophysicalenvironment can vary in scale from microscopic to global in extent.

DIFFRENCE B/W BIOTIC AND ABIOTIC

• Based on their origin, natural resources are classified into 1)Biotic:  Biotic resources are obtained from

the biosphere (living and organic material), such as forests, animals, birds, and fish and the materials that can be obtained from them. Fossil fuels such as coal and petroleum are also included in this category because they are formed from decayed organic matter.

2)Abiotic:  Abiotic resources are those that come from non-

living, non-organic material. Examples of abiotic resources include land, fresh water, air and heavy metals including ores such as gold, iron, copper, silver, etc.

NATURAL RESOURCES• Natural resources occur naturally within environments that exist

relatively undisturbed by mankind, in a natural form.• Some of them are essential for our survival while most are used for

satisfying our wants.• They are present abundantly in nature.• Natural resources are materials and components that can be found

within the environment. Every man-made product is composed of natural resources. A natural resource may exist as a separate entity such as fresh water, and air, as well as a living organism such as a fish, or it may exist in an alternate form which must be processed to obtain the resource such as metal ores, oil, and most forms of energy.

Organism

Population

Community

Biosphere

Ecosystem

Biosphere- The biosphere is the global sum of all ecosystems. It can also be termed the zone of life on Earth, a closed system (apart from solar and cosmic radiation and heat from the interior of the Earth), and largely self-regulating.

ECOSYSTEM-An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system.

Community- several interacting populations that inhabit a common environment and are interdependent.

Population-a group of organisms of one species living in the same place at the same time that interbreed and compete with each other for resources (ex. food, mates, shelter)

Organism- any unicellular or multicellular form exhibiting all of the characteristics of life, an individual.

•The lowest level of organization

FEEDING RELATIONSHIP

• The three basic ways in which organisms get food are as producers, consumers and decomposers.

• Producers (autotrophs) are typically plants or algae. Plants and algae do not usually eat other organisms, but pull nutrients from the soil or the ocean and manufacture their own food using photosynthesis. For this reason, they are calledprimary producers. In this way, it is energy from the sun that usually powers the base of the food chain. An exception occurs in deep-sea hydrothermal ecosystems, where there is no sunlight. Here primary producers manufacture food through a process

• called chemosynthesis.

• Consumers (heterotrophs) are species that cannot manufacture their own food and need to consume other organisms. Animals that eat primary producers (like plants) are called herbivores. Animals that eat other animals are calledcarnivores, and animals that eat both plant and other animals are called omnivores.

• Decomposers (detritivores) break down dead plant and animal material and wastes and release it again as energy and nutrients into the ecosystem for recycling. Decomposers, such as bacteria and fungi (mushrooms), feed on waste and dead matter, converting it into inorganic chemicals that can be recycled as mineral nutrients for plants to use again.

Symbiotic Relationships

Symbiosis- two species living together

3 Types of symbiosis:

1. Commensalism

2. Parasitism

3. Mutualism

Commensalism- In ecology, commensalism is a class of relationships between two organisms where one organism benefits from the other without affecting it. This is in contrast with mutualism, in which both organisms benefit from each other, amensalism, where one is harmed while the other is unaffected, and parasitism, where one benefits while the other is harmed.

Parasitism- Parasitism is a non-mutual symbiotic relationship between species, where one

species, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred primarily to organisms visible to the naked eye, or macroparasites (such as helminths). Parasitenow includes microparasites, which are typically smaller, such as protozoans,viruses and bacteria. Some examples of parasites include the plants mistletoe and cuscuta, and animals such as hookworms.

• Mutualism is the way two organisms of different species exist in a relationship in which each individual benefits from the activity of the other. Similar interactions within a species are known as co-operation. Mutualism can be contrasted with interspecific competition, in which each species experiences reduced fitness, and exploitation, or parasitism, in which one species benefits at the expense of the other. Mutualism is a type of symbiosis. Symbiosis is a broad category, defined to include relationships that are mutualistic, parasitic, orcommensal. Mutualism is only one type.

Trophic LevelsThe trophic level of an organism is the position it occupies in a food chain.

The word trophic derives from the Greek τροφή (trophē) referring to food or feeding. A food chain represents a succession of organisms that eat another organism and are, in turn, eaten themselves. The number of steps an organism is from the start of the chain is a measure of its trophic level. Food chains start at trophic level 1 with primary producers such as plants, move to herbivores at level 2, predators at level 3 and typically finish with carnivores or apex predators at level 4 or 5. The path along the chain can form either a one-way flow or a food "web". Ecological communities with higher biodiversity form more complex trophic paths.

Trophic Levels

Producers- Autotrophs

Primary consumers- Herbivores

Secondary consumers-small

carnivores

Tertiary consumers-

top carnivores

E

N

E

R

G

Y

Trophic LevelsFood chain- simple model that

shows how matter and energy move through an ecosystem

Toxins in food chains-

While energy decreases as it moves up the food chain, toxins increase in potency.

•This is called biological magnification

Ex: DDT & Bald Eagles

Trophic Levels

Food web- shows all possible feeding relationships in a community at each trophic level

•Represents a network of interconnected food chains

NUTRIENT CYCLE

• The nutrient cycle is nature's recycling system. All forms of recycling have feedback loops that use energy in the process of putting material resources back into use. Recycling in ecology is regulated to a large extent during the process of decomposition. Ecosystems employ biodiversity in the food webs that recycle natural materials, such as mineral nutrients, which includes water. Recycling in natural systems is one of the many ecosystem services that sustain and contribute to the well-being of human societies.

WATER CYCLE

• The water cycle, also known as the hydrologic cycle or the H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly constant over time but the partitioning of the water into the major reservoirs of ice, fresh water, saline water and atmospheric water is variable depending on a wide range of climatic variables. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In doing so, the water goes through different phases: liquid, solid (ice), and gas (vapor).

CARBON CYCLE

• The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere,pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Along with the nitrogen cycleand the water cycle, the carbon cycle comprises a sequence of events that are key to making the Earth capable of sustaining life; it describes the movement of carbon as it is recycled and reused throughout the biosphere.

• The global carbon budget is the balance of the exchanges (incomes and losses) of carbon between the carbon reservoirs or between one specific loop (e.g., atmosphere ,biosphere) of the carbon cycle. An examination of the carbon budget of a pool or reservoir can provide information about whether the pool or reservoir is functioning as a source or sink for carbon dioxide.

• The carbon cycle was initially discovered by Joseph Priestley and Antoine Lavoisier, and popularized by Humphry Davy.

NITROGEN CYCLE

• The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is nitrogen, making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramaticallyaltered the global nitrogen cycle.

NITROGEN FIXATION

• Atmospheric nitrogen must be processed, or "fixed", to be used by plants. Some fixation occurs in lightning strikes, but most fixation is done by free-living or symbiotic bacteria known as diazotrophs. These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia, which is converted by the bacteria into other organic compounds. Most biological nitrogen fixation occurs by the activity of Mo-nitrogenase, found in a wide variety of bacteria and some Archaea. Mo-nitrogenase is a complex two component enzyme that has multiple metal-containing prosthetic groups

Atmospheric nitrogenLightning

Nitrogen fixing

bacteria

Ammonium Nitrification by bacteria

Nitrites Nitrates

Denitrification by bacteria

Plants

Animals

Decomposers

Nitrogen Cycle