Biodiversity

Dr. Manish Semwal

The Biosphere• The sum of Earth’s ecosystems, the Biosphere

encompasses all parts of the planet inhabited by living things.

• In 2002 about 1.7 million species had been discovered and identified by biologists, although estimates of the true number of species on earth range from 3.6 to over 10 million (Wilson 2002).

• For at least 3.8 billion years, a complex web of life has been evolving here on Earth

Biome

• The term biome refers to a major type of terrestrial ecosystem that typifies a broad geographical region.

Biodiversity

• Biodiversity is an abundance of different life.

• Biodiversity (biological diversity) is the variety of all living organisms and their interactions. Scientists often speak of three levels of diversity - species, genetic, and ecosystem diversity.

Earth’s Biodiversity

751000

30800

24840026900

690005800 281000

InsectsProtozoa

Higher plantsAlgaeFungi

Bacteria & virusesOther animals

• "Biological diversity is the variety and variability among living organisms and the ecological complexes in which they occur.

• Genetic diversity is the combination of different genes found within a population of a single species, and the pattern of variation found within different populations of the same species. Coastal populations of Douglas fir are genetically different from Sierran populations

• Species diversity is the variety and abundance of different types of organisms which inhabit an area. A ten square mile area of Modoc County contains different species than does a similar sized area in San Bernardino County.

• Ecosystem diversity encompasses the variety of habitats that occur within a region, or the mosaic of patches found within a landscape. A familiar example is the variety of habitats and environmental parameters in an ecosystem and its grasslands, wetlands, rivers, estuaries, fresh and salt water."

• Reasons human cultures value biodiversity:

The rich variety of species in biological communities gives us food, wood, fibers, energy, raw materials, industrial chemicals, and medicines, all of which pour hundreds of millions of dollars into the world economy each year.

Moreover, people have a natural affinity for nature, a sense of “biophilia,” wherein they assign a non-utilitarian value to a tree, a forest, and wild species of all kinds

Importance of Biodiversity

Pollination For every third bite you take, you can thank a pollinator.

Air and Water PurificationBiodiversity maintains the air we breathe and the water we drink.

Climate ModificationBy giving off moisture through their leaves and providing shade,

plants help keep us and other animals cool.

Drought and Flood ControlPlant communities, especially forests and wetlands, help control

floods.

Cycling of NutrientsThe elements and compounds that sustain us are cycled endlessly

through living things and through the environment.

Importance HabitatNatural ecosystems provide habitat for the world’s species

(forests, wetlands, estuaries, lakes, and rivers – the world’s nurseries).

FoodAll of our food comes from other organisms.

Natural Pest Control ServicesNatural predators control potential and disease-carrying

organisms in the world.

Drugs and MedicinesLiving organisms provide us with many drugs and medicines.

Loss of Biodiversity Multiple forces entrained by human activity

reinforce one another and force species down. These factors are summarized by conservation biologists under the acronym HIPPO + G (Wilson 2002).

• Habitat Destruction• Invasive Species• Pollution• Population• Overharvesting• Global Warming

Threats: Invasive species

• A species that is not native to a region

• Threaten native species by taking over resources

Keystone species - a species which is CRITICAL to the functioning of an ecosystem

– Many different species are dependent on it– If lost, the entire ecosystem is destroyed

Zonation • Zonation is the classification of biomes into zones based on their

circulation or grouping in a habitat as influenced by environmental factors, such as altitude, latitude, temperature, other biotic factors

• Supplement• An example of ecological zonation is the vertical zonation of the pelagic

ocean:• epipelagic zone – the zone where photosynthetic organisms (such as

planktons) thrive as they require enough light for photosynthesis • mesopelagic zone – the zone under epipelagic zone where

nektons are abundant• bathypelagic zone – the zone near to the deep sea floor where benthos

abound

Succession

• the gradual and orderly process of change in an ecosystem brought about by the progressive replacement of one community by another until a stable climax is established

Examples of Changing Ecosystems

• A forest could have been a shallow lake a thousand years ago.

• Mosses, shrubs, and small trees cover the concrete of a demolished building.

Ecological Succession

• Gradual process of change and replacement of the types of species in a community.

• May take hundreds or thousands of years.

6/5/03 M-DCC / PCB 2340C 19

Primary Succession

• Newer communities make it harder for the older ones to survive.

• Example: Younger birch trees will have a harder time competing with taller, older birch trees for sun, but a shade loving tree may replace the smaller birch trees.

Primary Succession

• Type of succession that occurs where there was no ecosystem before.

• Occurs on rocks, cliffs, and sand dunes.

• Primary succession is very slow.• Begins where there is no soil.• Takes several hundred years to produce fertile

soil naturally.• First species to colonize bare rock would be

bacteria and lichens.

Lichens

• Do not require soil.• Colorful, flaky patches.• Composed of two species, a fungi and an

algae.• The algae photosynthesize and the fungi

absorbs nutrients from rocks and holds water.• Over time, they break down the rock.

• As the rocks breaks apart, water freezes and thaws on the cracks, which breaks up the rocks further.

• When the lichens die, they accumulate in the cracks.

• Then mosses begin to grow and die, leading to the creation of fertile soil.

• Fertile soil is made up of the broken rocks, decayed organisms, water, and air.

Mosses on rocks

• Primary succession can be seen happening on the sidewalks.

• If left alone, even NYC would return to a cement filled woodland.

Secondary Succession

• More common• Occurs on a surface where an ecosystem has

previously existed. • Occurs on ecosystems that have been

disturbed or disrupted by humans, animals, or by natural processes such as storms, floods, earthquakes, and volcanoes.

Secondary Succession: Mt. St. Helens

• Erupted in 1980.• 44,460 acres were

burned and flattened.• After the eruption, plants

began to colonize the volcanic debris.

• Pioneer species: the first organism to colonize any newly available area and begin the process of ecological succession.

• Over time, the pioneer species makes the area habitable by other species.

• Today, Mt. St. Helens in the process of secondary succession.• Plants, flowers, new trees and shrubs have started to grow.• If this continues, over time they will form a climax

community.

• Climax community: the final and stable community.

• Climax community will continue to change in small ways, but left undisturbed, it will remain the same through time.

Fire and Secondary Succession

• Natural fire caused by lightening are a necessary part of secondary succession.

• Some species of trees (ex: Jack pine) can only release their seeds after they have been exposed to the intense heat of a fire.

• Minor forest fires remove brush and deadwood.

Fire and Secondary Succession

• Some animals depend on fires because they feed on the newly sprouted vegetation.

• Foresters allow natural fires to burn unless they are a threat to human life or property.

Old-field Succession

• Occurs in farmland that has been abandoned.

• Grasses and weeds grow quickly, and produce many seeds that cover large areas.

• Over time, taller plants grow in the area, shading the light and keeping the pioneer species from receiving any light.

• The longer roots of the taller plants deprive the pioneer species from water.

• The pioneer species die.

• Taller trees begin to grow and deprive the taller plants of water and light.

• Followed by slow growing trees (oaks, maples) takeover the area.

• After about a century, the land returns to a climax community.