Cane Toad: An Unnatural History

• Learned about exotic, nonnative and invasive species the role thy play on native species and altering an ecosystem

Cane Toad – Team Think• Use this movie to learn about Evolution and

Biodiversity1. Describe the biomes that were in this video.2. What is biodiversity? Describe the biodiversity before and after the cane toads were introduced to Australia. - Give another example of biodiversity altered due to introduction to nonnative species3. Distinguish between , natural selection, artificial selection and genetic engineering.- Which of these took place in this movie? why?- Now, how would scientists use genetic engineering to “solve” the cane grub problem?

Biomes of Australia

Biodiversity – Huge-O Important-O• Provides us with:• Lots of ecosystem services• Natural resources (food, water, energy, medicines)• Natural service (air and water purification, soil

fertility,waster disposal,pest control)• Aesthetic pleasure

Earth is home to a tremendous diversity of

species

• Ecosystem diversity- the variety of ecosystems within a given region.

* Genetic diversity- the variety of genes within a given species.

* Species diversity- the variety of species within a given ecosystem.

Biodiversity - The variety of life living in an area.

Question:

The __________________ diverse an area

or species, the healthier and more

resilient it will be.

a. Less

b. More

More

Cane Toad Affects on Biodiversity?

• Freshwater crocodile population decreased (poisoned)

• Quolls taxa are at risk– to extinction in some regions of Australia (poisoned)

• Snakes – 49 taxa at risk (poisoned)• Frogs (via competition)• Some birds (poisoned)

How do we stop biodiversity loss• Assess what biodiversity is being lost• How it is being lost• Then attempt to establish a sustainable relationship

• 1. What effect did introducing the CaneToad to Australia have on the sugarcane grub as well as the Australia

• 2. What limitations might a scientists have on determining species diversity in this area?

• 1. If you were asked to manage this site for species diversity, what would you aim to do? How would you do it?

• Species richness- the number of species in a given area.

• Species evenness- the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals.

Measuring Biodiversity

Biodiversity• Diversity Increasers Diversity Decreasers – Diverse habitats– Disturbance in the habitat (fires, storms, etc.)– Environmental conditions with low variation– Environmental stress– Evolution– Extreme amounts of disturbance– Extreme environments– Extreme limitations in the supply of a fundamental resource– Geographic isolation– Introduction of species from other areas– Middle states of succession (habitat regrowth)– Trophic levels with high diversity

Biodiversity• Diversity Increasers Diversity Decreasers

• Diverse habitats• Disturbance in the

habitat (fires, storms, etc.)

• Environmental conditions with low variation

• Evolution• Middle states of

succession• Trophic levels with high

diversity

• Environmental stress• Extreme amounts of

disturbance• Extreme environments• Extreme limitations in

the supply of a fundamental resource

• Geographic isolation• Introduction of species

from other areas

What creates all this biodiversity?

•EVOLUTION!

Evolution is the mechanism underlying biodiversity

• Evolution- a change in the genetic composition of a population over time.

Fossils present but rare

Evolution and expansion of life

Fossils become abundant

Plants invade the land

Age of reptiles

Age of mammals

Insects and amphibians invade the land

Modern humans (Homo sapiens) appear about 2 seconds before midnight

Recorded human history begins 1/4 second before midnight

Origin of life (3.6–3.8 billion years ago)

Cane Toad – Team Think3. Distinguish between , natural selection, artificial selection and genetic engineering.- Which of these took place in this movie? why?- Now, how would scientists use genetic engineering

to “solve” the cane grub problem?

As far as we can tell, we are the only species that can value its diversity.

• Should we take care of it?• First, how will people later judge our generation if we do

not attempt to preserve a minimum of diversity, especially because we know perfectly well how to accomplish this?

• And second, as species adapt to each other, they form “a web of complex relations”, in which too much interruption might have unpredicted but severe consequences for human lives and society.

• Should these two reasons be sufficient to make our moral instinct – initially evolved to deal with kin and tribe – encompass nature’s diversity?

Evolution is the mechanism underlying biodiversity

• Evolution- a change in the genetic composition of a population over time.

• Microevolution- evolution below the species level.

• Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla.

Darwin’s theory of evolution by natural selection

• Individuals produce an excess of offspring.

• Not all offspring can survive.• Individuals differ in their traits.• Differences in traits can be passed on

from parents to offspring.• Differences in traits are associated with

differences in the ability to survive and reproduce.

Creating Genetic Diversity

• Genes- physical locations on chromosomes within each cell of an organism.

• Genotype- the complete set of genes in an individual.

• Mutation- a random change in the genetic code.

• Phenotype- the actual set of traits expressed in an individual.

Evolution by artificial and natural selection

• Evolution by artificial selection- when humans determine which individuals breed.

• Evolution by natural selection- the environment determines which individuals are most likely to survive and reproduce.

Evolution by Random Processes

• Mutation- occur randomly and can add to the genetic variation of a population.

• Genetic drift- change in the genetic composition of a population over time as a result of random mating.

• Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in its size.

• Founder effect- a change in a population descended from a small number of colonizing individuals.

The pace of evolution

Evolution shapes ecological niches and determines species distributions

• Range of tolerance- all species have an optimal environment in which it performs well. The limit to the abiotic conditions they can tolerate is known as the range of tolerance.

• Fundamental niche- the ideal conditions for a species.

Niches• Realized niche- the range of abiotic and

biotic conditions under which a species lives. This determines the species distribution, or areas of the world where it lives.

• Niche generalist- species that live under a wide range of conditions.

• Niche specialist- species that live only in specific habitats.

The Fossil Record

• Fossils- remains of organisms that have been preserved in rock. Much of what we know about evolution comes from the fossil record.

The Five Global Mass Extinctions

• Mass extinction- when large numbers of species went extinct over a relatively short period of time.

The Sixth Mass Extinction

• Scientists feel that we are in our sixth mass extinction, occurring in the last two decades.

• Estimates of extinction rates vary widely, from 2 % to 25% by 2020.

• In contrast to previous mass extinctions, scientists agree that this one is caused by humans.