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

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Insects

Protozoa

Higher plants

Algae

Fungi

Bacteria & viruses

Other 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

• 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.

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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.

Measuring Biodiversity• The simplest measure of biodiversity is the number of

species – called species richness.– Usually only count resident species, and not accidental or

temporary immigrants

• Another concept of species diversity is heterogeneity:

Community 1 Community 2

Species A 99 50

Species B 1 50

Heterogeneity is higher in a community where there are more species and when the species are more equally abundant.

Diversity Indices

• A mathematical measure of species diversity in a community.

• Reveals important information regarding rarity and commonness of species in a community.

Simpson’s Diversity Index

• Attempts to quantify the diversity (variety) of an ecosystem.

• There are two components:Evenness

Richness

Evenness

• Evenness is a measure of the relative abundance of the different species within an area.

• When the numbers of each type of species is even, the value for the Simpson Diversity Index will be larger.

Species richness

• Richness is a measure of the variety of the species

• More species is “richer” so the value for the index will be higher.

The equation

D = N(N - 1)

n(n -1)

D = diversity indexN = total number of organisms of all species

foundn = number of individuals of a particular species

The Simpson Diversity Index

• A high value of D suggests a stable and ancient site

• A low value of D could suggest pollution, recent colonization or agricultural management.

• The value of D indicates the richness and evenness of the species found within the area sampled.

Predict the value for D for the following: (high or low)

• Tropical rainforest

• Desert

• A wheat field

• A polluted river

• A tall grass prairie

How to Calculate D:

1. Record the numbers of each species2. Calculate n-1 for each species3. Find the total number of organisms, N4. Calculate the Simpson Diversity Index

D = N(N – 1) n(n -1)

Values for D

• What is the lowest possible value?

• What does a higher value indicate?

The values for D

• The lowest possible value is 1. When there is only one kind of species.

• This is a monoculture or an area that has been disturbed by pollution, a flood, or another big event

• A high value for D indicates stability, complexity and an older ecosystem.

Calculate the Simpson’s Diversity Index for each sample

Comment on the evenness and richness of each sample.

Answers

• Sample One: 2.99

• Sample Two: 1.15

• Both have the same richness as there are three species in each area.

• Sample One is more diverse because the species are more even.

Sampling Methods

• Transects and Quadrants– Plants and Non-motile animals

• Lincoln Index• Capture –Mark- Recapture

– Small animals

• Aerial observations– Large trees and animals

Average Size

• Measure all trees in a transect or quadrat.

• Produce a size-frequency histogram to show the size distribution.

• Can also calculate the average size tree.

Quadrat Sampling• Randomly select plots and

count all individuals in that plot.

• Each quadrat = 200m2.

• Can calculate density as #/m2 then multiply by total area to estimate the total # of trees.

• 60,703 m2 = 15 acres

Quadrat Species No.1 BoxElder 01 Button Bush 21 Chinese Tallow 11 Cottonwood 91 Maple 01 Willow 622 BoxElder 42 Button Bush 02 Chinese Tallow 02 Cottonwood 12 Maple 22 Willow 60

Transect Sample

• Randomly select a transect of known area and count every tree in that transect.

• Each transect = 90m2.

• Can calculate density for each tree species.

• 60,703 m2 = 15 acres

Sampling along Transects

• Samples taken at fixed intervals• Set up along an environmental gradient (e.g.

high to low on a mountain)

Line transect method

• A measured line laid across the area in the direction of the environmental gradient

• All species touching the line are be recorded along the whole length of the line or at specific points along the line

• Measures presence or absence of species

Belt transect method

• Transect line is laid out and a quadrant is placed at each survey interval

• Samples are identified and abundance is estimated– Animals are collected– For plants an percent coverage is estimated

• Data collection should be completed by an individual as estimates can vary person to person

Quadrats

• Used to measure coverage and abundance of plants or animals

• A grid of known size is laid out and all the organisms within each square are counted.

Lincoln Index

• Capture-Mark-Recapture– Animals are captured,counted, tagged and released.– After a period of time another capture occurs.– Previously tagged animals are counted and unmarked

organisms are marked. – Abundance is calculated using the following formula:

n1 x n2

n3

n1=total marked after catch 1

n2=total marked after catch 2

n3=total caught in catch 2 but marked in catch 1

Measurements

• Sampling methods measure – Density– Coverage– Frequency– Biomass– Diversity

Measuring Biodiversity• The simplest measure of biodiversity is the number of

species – called species richness.– Usually only count resident species, and not accidental or

temporary immigrants

• Another concept of species diversity is heterogeneity:

Community 1 Community 2

Species A 99 50

Species B 1 50

Heterogeneity is higher in a community where there are more species and when the species are more equally abundant.

Diversity Indices

• A mathematical measure of species diversity in a community.

• Reveals important information regarding rarity and commonness of species in a community.