L4 Processes in the biosphere

What is a biosphere?

• Biosphere: part of Earth in which life exists including all living and non-living parts (land, water, and air)

The biosphere consists of several physical layers that contain…

• Air

• Water

• Soil

• Minerals

• Life

Levels of organization

in the biosphere:

• biome

• ecosystems

• communities

• population

• individual

Ecotone

• A region containing a mixture of species from adjacent ecosystems and often species not found

in either of the bordering ecosystems.

• A transitional zone between ecosystems

What sustains life on earth?

• Energy from the sun through materials and living things in food webs then into the environment as long as low quality energy (mostly heat) and then back into space as heat

• The earth is an OPEN system from energy

• The Cycling of matter through parts of the biosphere.

  The earth is a CLOSED system for matter.

Gravity

• which allows the planet to hold on to its atmosphere and causes the downward movement of chemicals in the matter cycles.

ENERGY FLOW AND BIOGEOCHEMICAL CYCLES

• An ecosystem survives by a combination of energy flow and matter recycling.

What is energy flow?

Energy flow is the flow of energy through living things within an ecosystem.

Biogeochemical cycles

• The biogeochemical cycle involves the movement of elements and compounds among the land (lithosphere), organisms, air (atmosphere) and the oceans (hydrosphere).

• Human activities can affect these cycles

Producers or autotrophs

• Make their own food from compounds obtained from their environment.

ex: green plants on land, algae and plants near shorelines, phytoplankton in open water

• Most producers capture sunlight to produce carbohydrates by photosynthesis.

• But…..Some organisms such as deep ocean bacteria draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulphide (H2S) gas. (chemosynthesis)

Anaerobic respiration or fermentation:

• Some decomposers get energy by breaking down glucose (or other organic compounds) in the absence of oxygen.

• The end products vary based on the chemical reaction

• Methane gas

• Ethyl alcohol

• Acetic acid

• Hydrogen sulfide

Type of heterotrophs

that consume organic material for energy, relying on other organisms for food.

Herbivores

consume only plants

Omnivores

consume both plants and animals

Detritivores

consume plant and animal remains (earthworms, mites, crabs)

Decomposer

breaks down organic matter to obtain energy (bacteria & fungi)

Energy flow in ecosystem

• Energy in an ecosystem flows in one direction (from sun to the heterotrophs)

• Food chain- a series of steps in which organisms transfer energy by eating and being eaten

• Only about 10% of energy is transferred to organisms at the next trophic level: 10% --> 1% --> 0.1%

Ecological efficiency

• Percentage of useable energy transferred as biomass from one trophic level to the next.

Gross primary production (GPP)

Rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass.

Biomass

the dry weight of all organic matter contained in the organisms at

each trophic level in a food chain or web.

Net primary production (NPP)

• is the amount of biomass or carbon produced by primary producers per unit area and time.

NPP = GPP – R

• Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R).

Nature’s three most productive and three least productive systems

Terrestrial and aquatic

• swamps and marshes, tropical rainforest, temperate forest

• Estuaries, lakes and streams, continental shelf

Key questions for biomes and biodiversity

• WHY should we protect the planet’s biological diversity?

….but first, a look at the world’s major biomes

• HOW should we protect the planet’s biological diversity?

What is a biome

are broad types of biological, flora and fauna, communities with characteristic types of environments that occur in different conditions of temperature and precipitation.

5 major types of biomes

Tundra, desert, grassland, forest, aquatic

Tropical Rainforests have a Moisture Surplus

Tropical rainforests occur where rainfall is abundant—more than 200 cm (80 in.) per year— and temperatures are warm to hot year-round.

Tropical Savannas and Grasslands are Dry Most of the Year

• Primary plant life is grass. Occurs in variety of climates.

• Where there is too little rainfall to support forests, we find open grasslands or grasslands with often sparse tree cover, which we call savannas.

Deserts are Hot or Cold, but Always Dry

• Arid environment, little precipitation, four types: hot, semi-arid, coastal, and cold

• Deserts occur where precipitation is uncommon and slight, usually with less than 30 cm of rain per year.

Temperate Grasslands have Rich Soils

• As in tropical latitudes, temperate (midlatitude) grasslands occur where there is enough rain to support abundant grass but not enough for forests.

Temperate Forests can be Evergreen or Deciduous

• Include deciduous forests and rain forests. Temperate deciduous forests have hot summers and cold winters. Deciduous trees are the dominant plant species

• These forests are grouped by tree type, broad-leaved deciduous (losing leaves seasonally) or evergreen coniferous (cone-bearing).

Temperate Rainforests

• Warm temperatures, abundant precipitation all year, lush forests

• The coniferous forests of the Pacific coast grow in extremely wet conditions. The wettest coastal forests are known as temperate rainforest, a cool, rainy forest often enshrouded in fog.

Boreal Forests (Taiga) Lie North of the Temperate Zone

• Because conifers (針葉樹) can survive winter cold, they tend to dominate the boreal forest.

• Boreal forests are found in Siberia, Canada, and the western United States.

Tundra Can Freeze in Any Month

• Far northern latitudes with long winters (10 months) limited precipitation, permafrost

• Compared to other biomes, tundra has relatively low diversity.

• Temperatures are below freezing most of the year, making water unavailable to plants.

• Tundra occurs at high latitudes or on mountaintops.

Ecological diversity

different habitats, niches, species interactions

Species diversity

different kinds of organisms, relationships among species

Genetic diversity

different genes & combinations of genes within populations

What happens when the species population gets too small?

It can lead to inbreeding depression, reduced genetic diversity, and increased vulnerability to extinction.

Biodiversity hot spots

• Most of the world’s biodiversity concentrations are near the equator, especially tropical rainforests and coral reefs.

• Of all the world’s species, only 10 to 15 percent live in North America and Europe.

• Many of the organisms in megadiversity countries have never been studied by scientists.

Why should we protect the planet’s biological diversity?

What threatens biodiversity?

Habitat destruction, climate change, invasive species, and overexploitation.

BENEFITS OF BIODIVERSITY: ECOSYSTEM STABILITY

• High diversity may help biological communities withstand environmental stress better and recover more quickly than those with fewer species

• Keystone species: Sometimes, removing just one key species can severely disrupt the ecological balance

• Maintaining biodiversity is essential to preserving ecological services

ex: Food, Medicine, Aesthetic and Existence Values

What threatens biodiversity?

• Extinction, the elimination of a species, is a normal process of the natural world

• However, we are in the midst of a sixth wave of mass extinction (the Anthropocene?)

Current threats

• Habitat destruction

• Fragmentation

• Invasive species

• Pollution

• Human population growth

• Overharvesting

• Predator and pest control

To stop it we must

• Stop overharvesting

• Sustainable yield

• Hunting & fishing laws (every state?) in developing nations?

• Protect habitat

• Refuges, parks, preserves

• Endangered Species Act

McArthur & Wilson “Theory of Island Biogeography”

• colonization rate

• extinction rate (local)

• generation of new species

Island Biogeography

• Island size predicts number of species

• Everyplace is an island

• Habitat fragmentation

• Smaller fragments hold fewer species

Amazon Rainforest

• 20 million people

• 60-70% urban

• 500k indigenous (a hotspot for cultural diversity)

• Contains largest rainforest in world (1.4 billion acres)

• Most biodiverse area in the world

• Largest carbon sink

Settling the frontier

• building roads

• timber harvesting

• slash and burn agriculture (shifting cultivation)

• burning the remaining forest

• large scale agriculture and cattle ranching

• making the land productive “Most deforestation is occurring due to conversion for agriculture and cattle”

PROTECTINGTHE FRONTIER:AMAZON REGION PROTECTED AREAS PROGRAM (ARPA)

• ARPA sets aside vast tracts of land for both preservation and sustainable use.

• Works with local communities

• Deforestation has increased in recent years due to rising commodity prices and a weakening of the Forest