Chapter 47: The Biosphere

Section 1:

Earth: A Living Planet

Earth: A Living Planet

• Ecology is the study of the interactions of organisms with one another and with their physical surroundings

• Scientists who study ecology are called ecologists

• Earth is a single living system, also known as a biosphere, or living globe

A fast-moving stream in Gatlinburg, TN is an example of how organisms interact with one another and with their physical surroundings. The spray from the stream made it possible for mosses to grow on the surfaces of nearby boulders

Earth: A Living Planet

• The biosphere is that part of the Earth in which life exists– Includes all areas of land, air, and water on the

planet, as well as all the life that populates these areas

– Extends from about 8km above Earth’s surface to as far as 8km below the surface of the ocean

– Organisms are not distributed evenly throughout the biosphere

Ecosystems

• Because the biosphere is large, ecologists like to work with smaller units called ecosystems

• An ecosystem consists of a given area’s physical features (abiotic factors) and living organisms (biotic factors)– Abiotic factors – water, sunlight, soil type, rocks,

temperature, humidity, elevation, and rainfall– Biotic factors – fish, frogs, insects, snails, worms,

trees, ferns, lilies• The organisms living together in an ecosystem are often

referred to as a community

Ecological Succession

• Ecosystems change over time because every organism affects environmental conditions around it

• In the process of ecological succession an existing community of organisms is replaced by a different community over periods of time ranging from a few decades to thousands of years

Ecological Succession

• Sometimes succession occurs in places where no living community existed before

• When a new volcanic island arises from the sea, its newly cooled lava contains no life

• Organisms that colonize such areas are called pioneer species

• Succession can dramatically transform an ecosystem• Over time, a lake or pond may fill up with silt and

organic matter, turning first into a marsh and then into dry land

Ecological Succession

• As physical factors change, living communities also change

• Succession can also occur in places where natural disasters or human activities wipe out existing communities

• In much of the United States, for example, abandoned farmland is colonized first by grasses, then by other weeds, and later by shrubs and small trees

• Succession often leads to a fairly stable collection of organisms called a climax community

Ecological Succession

• An area’s climax community is due partly to chance

• An ecosystem may eventually return to the way it was after trees are cut down, land is dug up for mining, or any other kind of environmental damage occurs

• But, it is also possible that succession will take a different path and things will never be the same again

Chapter 47: The Biosphere

Section 2:

Land Biomes

Land Biomes

• A biome is an environment that has a characteristic climax community

• The Earth is made up of two main types of biomes: land biomes and aquatic biomes

• Most land biomes are named for their climax community, or the dominant type of plant life

Tundra

• Climate = cold, long winters and cool, short summers, with little precipitation

• Yearly precipitation = 10 inches• Covers 1/5 of Earth’s land surface• Annual precipitation is low• H2O is unavailable most of the year• Ground is permanently frozen• Grasses, sedges, dwarf willows, mosses• Foxes, reindeer, owls, caribou

Taiga

• Climate = cool, short summers and cold, long winters

• Yearly precipitation = 8 – 24 inches• Ideal conditions for needle-leaved trees• One of the largest biomes on Earth• Marshes, lakes, and ponds are common• Pine trees, fir trees, birch trees• Elk, moose, deer, wolves, bears, wolverines

Temperate Deciduous Forests

• Climate = warms summers and cool to cold winters• Yearly precipitation = 30 – 100 inches• Trees shed their leaves in the fall• Precipitation is distributed evenly throughout the

year• Contains humus ( a layer of decaying leaves and

twigs)• Deer, bears, beavers, raccoons, moose• Oak trees, hickory trees, beech trees, shrubs

Grasslands

• Climate = dry, hot summers and cold winters

• Yearly precipitation = 4 – 24 inches

• Agricultural land

• Populated by herds of grazing mammals– Impala, wildebeests, elephants

• Grasses, trees, shrubs, crops

Tropical Rain Forests

• Climate = warm and moist, with little variation in either rainfall or temperature

• Yearly precipitation = 100 inches• Most diverse biome• ½ of Earth’s species are here• Most will be gone within 40 years• Leads to the extinction of large numbers of species• Lush plants, trees• Butterflies, monkeys, insects

Deserts

• Climate = very dry, often hot• Yearly precipitation = 8 inches• Organisms have features that allows them to

conserve water• Vegetation is sparse• Less than 5% of North America is desert• Creosote brushes, cacti• Roadrunners, kangaroo rats, kit foxes

Chapter 47: The Biosphere

Section 3:

Aquatic Biomes

Aquatic Biomes

• Water ecosystems• Includes freshwater, marine, and estuaries• These biomes support more organisms than do the

land biomes• Some of the abiotic factors that affect the kinds

of organisms found in the aquatic biomes are light intensity, amounts of oxygen and carbon dioxide dissolved in the water, and the availability of organic and inorganic nutrients

Freshwater Biomes

• Rivers, streams, and lakes are considered the freshwater biomes of the Earth

• They provide much of our drinking water and are an important source of food

• Tiny floating plants and animals drift and swim through the water

• These organisms are eaten by fish and amphibians, which also eat the vegetation and insects that fall into the water from overhanging trees

Freshwater Biomes

• Contains insects, fish, amphibians, reptiles, and mammals

• Unfortunately, people all over the world are using rivers and lakes as dumping grounds for wastes

• The results of this carelessness are beginning to catch up with us

In swift-moving rivers, most organisms live in the shallows, where algae and mosses cling to the surfaces of rocks.

Marine Biomes

• The vast habitats of the ocean, or the marine biomes, cover most of the surface of Earth

• Photosynthesis can only take place in the uppermost region of a marine biome

• This region is called the photic zone– May be as shallow as 30m or as deep as

200m– Phytoplankton and algae grow here

Marine Biomes

• Oceanographers have divided marine biomes into distinct zones based on their depth and distance from the shore

• Each of these zones contains organisms that are adapted to the conditions there

Intertidal Zone

• Most difficult zone for organisms to live in• Must tolerate radical changes in their surroundings

– Once or twice a day they are submerged in ocean water– The remainder of the time they are exposed to air and

sunlight– Organisms here have adapted in some way to the

pounding and crashing of waves– Some organisms burrow into the sand to keep from

being washed out to sea– Others attach themselves to rocks

The intertidal zone is characterized by organisms such as barnacles and starfish.

Neritic Zone

• Extends from the low-tide line to the edge of the open sea

• Large seaweed are abundant here because this part of the ocean is the photic zone

• In shallow areas of tropical waters, meadows of turtle grass provide food for fish, invertebrates, and turtles

• Along the ocean floor, lobsters and crabs crawl while flounder and rays swim above them

The neritic zone provides a home to brilliantly colored coral-reef fishes.

Open-Sea Zone

• Phytoplankton are responsible for 80-90% of the Earth’s photosynthetic activity

• Phytoplankton are eaten by larger animals

• Thus the chain of life in the sea begins with these tiny organisms

• Swimming rapidly through the open-sea zone are fish of all shapes and sizes and mammals such as dolphins and whales

Open-Sea Zone

• Because nutrients are scarce in most of the open sea, the growth of phytoplankton is relatively slow

• This limits the number of animals that can live there• Closer to the shore, however, nutrients are more

abundant, and countless fish swim there to feed and reproduce

• Unfortunately, these rich fishing areas are much more susceptible to pollution than is the open sea

Deep-Sea Zone

• Area of high pressure, cold temperature, and total darkness

• This area is home to some of Earth’s strangest creatures

• Here, zooplankton wait for night in order to migrate to the ocean’s surface and feed on phytoplankton

• Herds of bottom dwellers crawl along on the ocean floor

The deep-sea zone is home to some of the Earth’s most bizarre creatures. The tube worms belong to an ecological community whose ultimate source of energy is chemicals from volcanic vents.

Estuaries

• Estuaries are found at the boundary between fresh water and salt water

• Salt marshes, mangrove swamps, lagoons, and the mouths of rivers that empty into the ocean are examples of estuaries

• Estuaries support a variety of life forms

• Because estuaries are usually shallow, sunlight is able to penetrate the water completely

Estuaries

• Photosynthesis occurs at all levels, making estuaries a suitable environment for aquatic plants

• The abundance of such plants, in turn, supports many types of fish, shrimp, and crabs

• In fact, many fish and invertebrates spawn, hatch, and nurse their young in estuaries

• As the young mature, they head for open sea, then return to the estuaries to reproduce

• Several species of birds use estuaries for nesting, feeding, and resting

Estuaries are areas where fresh water and salt water meet. This salt marsh in Long Island, New York and the mangrove swamp in Florida are examples of estuaries.

Chapter 47: The Biosphere

Section 4:

Energy and Nutrients: Building the Web of Life

Energy and Nutrients: Building the Web of Life

• One of the most important factors in any ecosystem is the flow of energy through the ecosystem

• Approximately ½ of the energy plants absorb from the sun is used immediately

• The rest is stored in plant tissues in the form of carbohydrates

• Animals that eat the plants obtain this energy

Energy and Nutrients: Building the Web of Life

• Energy cannot be recycled, or used again• Thus energy in an ecosystem is referred to as a

flow rather than a cycle• Nutrients are generally recycled through an

ecosystem• When an animal dies, its matter does not

disappear• Rather, it decomposes and eventually gets used

by another organism

Organisms are classified as producers, consumers, or decomposers, depending on how they get their food. Because spruce budworms feed directly on the jack pine, which is a producer, they are called primary consumers. Robins, which feed on worms, are called secondary consumers. Decomposers, such as mushrooms, get their food from the remains of dead organisms.

The Flow of Energy

• The sun is the ultimate source of energy for all living things

• Because photosynthetic organisms are able to make their own food from inorganic substances, they are called producers

• Animals, on the other hand, are consumers

• Consumers get their energy either directly or indirectly from producers

The Flow of Energy

• Consumers that feed directly on producers are called primary consumers– Herbivores

• Consumers that feed on primary consumers are called secondary consumers– Carnivores

• Energy flows through an ecosystem from the sun to producers and then to consumers

The Flow of Energy

• When plants and animals in an ecosystem die, their remains do not build up because of the presence of decomposers

• Decomposers are organisms that obtain their energy from nonliving organic matter

• Each step in this series of organisms eating other organisms is called a trophic, or feeding, level

The Flow of Energy

• At each higher trophic level, less and less of the energy originally captured by the producers is available

• Approximately 10% of the energy at one trophic level can be used by animals at the next trophic level

• At each successive trophic level, less energy is available to an organism

Ecological Pyramids

• Ecologists use ecological pyramids to represent the energy relationships among trophic levels

• There are three types of ecological pyramids

– Pyramid of energy

– Pyramid of biomass

– Pyramid of numbers

Pyramid of Energy

• A pyramid of energy shows the total amount of incoming energy at each successive level

Pyramid of Biomass

• The trophic levels of an ecosystem can also be represented by a pyramid of biomass, which shows the total mass of living tissue at each level

Pyramid of Numbers

• Relationships among trophic levels may also be represented by a pyramid of numbers

• A pyramid of numbers illustrates the total number of organisms at each level

Biogeochemical Cycles

• Although energy moves in a one-way direction through an ecosystem, nutrients are recycled

• All organisms require certain essential nutrients in order to grow

• As members of each trophic level eat members of the level beneath them, they acquire the complex organic molecules and elements they need in addition to energy

• Nutrients move through the biosphere in a series of physical and biological processes called biogeochemical, or nutrient, cycles

The Water Cycle

• The movement of water from the atmosphere to the Earth and back to the atmosphere is called the water cycle

• The water cycle consists of an alternation of evaporation and condensation

• Water molecules enter the air by evaporation from the ocean and other bodies of water

• In the air, water molecules condense and then return to the Earth in the form of precipitation

The Water Cycle

• On land, most of the rainwater runs along the surface of the ground until it enters a river or stream that carries it to a larger body of water

• Some water sinks into the ground and is called groundwater

• The upper surface of groundwater is known as the water table

The Water Cycle

The Nitrogen Cycle

• All organisms require nitrogen to build proteins

• The movement of nitrogen through the biosphere is called the nitrogen cycle

• However, most of the nitrogen cannot be directly used by living things

• It must be converted into other forms

The Nitrogen Cycle• Certain bacteria that live on roots of plants change

free nitrogen in the atmosphere into nitrogen compounds that can be used by living things– Nitrogen fixation

• Once the nitrogen compounds are available, plants use them to make plant proteins

• Animals then eat the plants and use the proteins to make animal proteins

• When the plants and animals die, the nitrogen compounds return to the soil

The Nitrogen Cycle

• Eventually other bacteria in the soil break down these nitrogen compounds into free nitrogen in a process called denitrification

• These bacteria are called denitrifying bacteria

• Through the process of denitrification, free nitrogen is returned to the atmosphere

The Nitrogen Cycle

The Carbon and Oxygen Cycles

• The process by which carbon is moved through the environment is called the carbon cycle

• During photosynthesis, green plants and algae use carbon dioxide from the atmosphere to form glucose

• Consumers and decomposers use glucose in respiration, during which they produce carbon dioxide

• Carbon dioxide is then released into the atmosphere, completing the carbon cycle

The Carbon and Oxygen Cycles

• The movement of oxygen through the environment is called the oxygen cycle

• During photosynthesis, water molecules are split, releasing oxygen into the atmosphere

• The oxygen is used by most organisms for respiration

• During respiration, water is released• The water is absorbed by plants, and the cycle

begins again

The Carbon Cycle

The Oxygen Cycle

Nutrient Limitation

• The rate at which producers can capture energy and use it to produce living tissue is controlled be several factors, one of which is the amount of available nutrients

• If a nutrient is in short supply – thus limiting an organism’s growth – it is called a limiting factor

Feeding Relationships

• The simplest feeding relationship is a food chain

• In one food chain, a big fish eats little fish that eat tiny fish that eat plankton

• Nature is almost never that simple• Instead of using a food chain, which only

shows one feeding level, ecologists use food webs

• Food webs have many crisscrossing strands