We’ve already learned through example and models why biodiversity is important. Let’s define the various types of biodiversity, however, since there are many:

• Species Diversity

• Ecosystem diversity

• Functional diversity

• Genetic diversity

• Cultural diversity

The most commonly thought of biodiversity, and that is simply defined as the species “richness” or the variety of species in an area.

This refers to the variety of defined ecosystems within an area, such as deserts, grasslands, forests, and such. It also refers to the number of communities and populations in an area as well.

Refers to the variety of processes such as matter and energy cycling that is accomplished in ecosystems on Earth. (including nutrient cycles and food webs)

Refers to the variety of genes within a species, which dictate the characteristics of the organisms that possess them…and

Refers to the variety of human cultures, and attributes of human cultures which help humans adapt to changing conditions.

• Supplies us with food, wood, fibers, medicines, and energy

• Preserving the quality of our water and air

• Maintaining the fertility of the soils

• Disposal of wastes

• Control populations of pests

We’ve already spent a good deal of time evaluating the importance of biodiversity. Let’s remind ourselves exactly what biodiversity is…

• The variety of the Earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life.

So…just where did all these organisms come from, and how did this biodiversity happen?

So far, scientists have identified 1.8 million of Earth’s 4-100 million species.

Kingdoms Eubacteria, and Archaebacteria…10,500 species

Kingdom Protista…250,000 species

fly agarics mushroom

Kingdom Fungi, 50,000 species

Kingdom Plantae, 250,000 species

Kingdom Animalia, 1,000,000 species

There are few things in science that are as controversial as the origins of life, but the fact is that however it started, it has persisted on Earth for nearly 3.8 billion years! As scientists speculate that the first life on Earth was Prokaryotic…just how did such diversification occur?

Fossil StromatolitesCurrent Stromatolites

Complex Multicellular Heterotrophs

The work done in the 1800s by Charles Darwin, and Alfred Wallace helped to explain how this all happened.

• There is a struggle for existence (competition for resources) in populations that contain many variations.

• Those that outcompete others in a population, survive and pass those traits that helped them, along to their offspring

• Those that compete unsuccessfully, die and don’t pass their traits along.

• Over time, advantageous traits are selected for naturally…which is why we call this process… Natural Selection

• Similar organism reproduce similar organisms. A dog reproduces a dog, and a dandelion reproduces a dandelion.• Often, the number of offspring is overproduced: The number that survive is less than that initially reproduced.• Individual organisms must compete with each other and with other species for limited resources in the environment (food, water, space, mates…etc)• In any population, individuals vary with respect to any given trait (height, skin color patterns, size, speed)• Some variations are favorable (make those individuals more likely to be successful at reproduction, than those with unfavorable traits)• Those organisms with favorable traits will survive and pass those traits on to their offspring. Those with unfavorable traits will die and not pass on their traits (NATURAL SELECTION)• Given sufficient time, because natural selection will accumulate these favorable traits, the species will change or evolve.

A Closer Look at Natural Selection…A Closer Look at Natural Selection…

Stromatolites: A record of the oldest life on Earth…

Fossil Stromatolites

Most of what we know about prehistoric life comes from fossilized evidence of its existence. Fossils are mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, seeds…or even impressions left by such items and preserved in rock.

Teleoceras: Fossilized Rhino

The fossil record is incomplete. Why?

Some animals don’t leave fossils behind. Still others have been destroyed by the rock cycle.

The work of piecing together evidence of past life from fossils is done by the Paleontologist

How do species evolve?

• Natural Selection

• Genetic Drift

The environment in which an organism lives determines what traits or variations are favorable

Slight random changes in the genetic makeup of a population over time

This genetic variability is created by chance mutations in genes of organisms, while DNA is replicating.

I hope this molecule looks familiar!

Some of these “errors” can occur when the cells are exposed to agents that cause mutations…called “mutagens”….such as UV radiation.

While mutations can occur in any cell in the body (somatic), it is the mutations that occur in the sex cells that enable those mutations to be passed on to the next generation.

What characteristics have allowed humans to dominate Earth the way they have?

Opposable Thumb

Walking Upright

Complex Brain

While humans are not by any means excluded from the chances of extinction, our brains may indeed be our most advantageous adaptation…to help us find ways to cope with the changes in the environment (which we are largely causing) that most organisms would find intolerable, and impossible to adapt to.

Will humans be able to adapt to future environmental probabilities? Probably because…

Nature will only select advantageous traits that already exist in a population, or that are likely to be created by mutations.

Even if that trait is present, reproductive capacity may hold back the evolutionary tendency

Organisms with very short life cycles are far more capable of producing the variations necessary for rapid evolution, as opposed to those who only produce 1-4 offspring during their lifetimes

The Earth today looks nothing like it did when it formed, and it continues to change dramatically every day. Earth’s molten mantle, which lies beneath the crust, is constantly moving the hardened plates around through convection currents.This becomes important as to the placement of organisms, because where oceans and land are located greatly influences environmental conditions. When these plates carrying the continents separate and/or fuse together, new environmental conditions arise, setting up new circumstances for organisms. This gives them the opportunity to adapt, migrate, or become extinct.

Throughout Earth’s Geologic History, the environments have changed greatly.

• Hot and dry at the end of the Permian

• Snowball Earth (Proterozoic Eon)

• High oxygen

• High CO2

• Meteorite

impacts Gorgonopsid in Permian Desert

A high degree of genetic biodiversity allowed life to continue on this planet that is constantly changing!

When natural selection leads to an entirely new species, a process called “speciation” has occurred. Speciation can occur in a number of ways:

A species may become Geographically Isolated

Any time a population of organisms becomes “isolated” they have the chance to “diverge” from the other population.Places on Earth that have been “isolated” for long periods of time, have developed really diverse and “unique” species.

A Species is Reproductively IsolatedOccurs when something acts to prevent organisms from reproducing together, and is usually driven by the females of a species.

A natural process which affects the levels of biodiversity on Earth is extinction. Extinction occurs when the last surviving individual of a species is gone.

Determining the exact moment of extinction is difficult, and is often determined retrospectively. Sometimes the reproductive potential of a species ceases before the last individual actually dies.

Takahe in New Zealand

Every day about 137 species become extinct. That’s over 50,000 species every year!

The most vulnerable species are “endemics”, who are only found in one area.

• Amphibians

Coqui

Panamanian golden frog

Blue Poison Dart Frog of Surinam

The fossil record indicates that a low rate extinction (or background extinction) occurs when one to five species becomes extinct for each million or so species on Earth…whereas a Mass Extinction occurs when there is a significant rise above background level.

Mass extinctions occur when global catastrophic events cause large groups of species (25-70%) to be wiped out, in a geological period lasting up to 5 million years. Mass extinction periods also are marked by low speciation rates as well.

The one plus that occurs during periods of mass extinction is that it gives new species the opportunity to fill the habitats and niches left by the now extinct organisms.

Each species in an ecosystem plays a role, also known as an “ecological niche”. A niche can be anything from dietary needs

of organisms, temperature needs, or amount of daylight, or darkness that they need. A niche may also include mating and reproductive patterns

Niche is not to be confused with habitat, which is where an organism lives.

Niches are used to help define species as either “generalists” or “specialists”.

The narrower the niche, the more prone to extinction a species is.

Roaches, the great generalists

Native species are those which are indigenous, or that normally live in an ecosystem.

American Elm in Fort Worth

Tree of Heaven Nonnatives are also known as invasive, or exotic species

Indicator species are those which are used as a “gauge” by ecologists to determine the health, or degree of ecological danger in an ecosystem.

Giant Swallowtail Butterfly

Lichens

Just as keystones are the most important factor that hold arches together, keystone species have a great affect on the types and abundance of other species in an ecosystem.

Remove the keystone, and the arch tumbles

Black-Tailed Prairie Dogs

Bald and golden eagles, swift foxes, coyotes, ferruginous hawks, burrowing owls, badgers and black-footed ferrets, countless insects and other invertebrates, as well as plants also rely on Prairie Dogs and their activities.

Foundation species actually “build” ecosystems, literally providing the “foundation” for the community.

North American Bison

Many keystone species are prone to extinction because of small populations, which leads to a cascade effect.

Each of you will produce a three-slide PowerPoint/Prezi/ or some other multi-media presentation…to be uploaded to NetSchool. Each person will become an expert on one extinct, and one endangered organism, and be prepared to discuss and answer questions after their presentations. Each person’s presentation must have imported graphics/pictures/animation, and:

Slide One:

Highlight one species that has become extinct on Earth (with picture)

When?

Why…what were the circumstances?

What niche did they fill in their ecosystem?

What was their habitat like?

Were they keystone species, or foundation? Etc…Slide Two:

Tell how the extinction of that species impacted/affected/ caused a cascade effect in their ecosystem, or impacted at least two other organisms

Slide Three:

Choose an endangered species, and predict what would happen in their ecosystem if they were to become extinct.