Natural Selection

Natural Selection

What is natural selection? In 1858, Darwin and Alfred Russell proposed the

same explanation for how evolution occurs In his book, Origin of the Species, Darwin

proposed that evolution occurs by natural selection

Natural selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species

Natural Selection

What is natural selection? Factors that affect natural selection

Overproduction – Most species produce far more offspring than can survive

There are not enough resources – food, water, living space, for them all to survive

Natural Selection Type I curves

High age-specific survival probability in early and middle life,

Rapid decline in survival in later life. Humans, large mammals

Type II curves Between Types I and III Constant mortality rate/survival probability is

experienced Some birds and some lizards.

In Type III curves Greatest mortality is experienced early in life Low rates of death for those surviving this bottleneck. Insects, marine organisms

Natural Selection

What is natural selection? Formation of new species

Isolation can cause a new species can form. Over a long period of time, an isolated group of

individuals of a species can evolve different traits that prevent reproduction

Natural Selection

What is natural selection? Variation – a difference between individuals of

the same species Competition – organisms compete to survive

since they must compete for living space, water and food

Selection – some individuals are better suited for their environment

Environmental change – a change in the environment can affect an organism’s ability to survive and therefore lead to natural selection

Natural Selection

What is natural selection? Darwin proposed that, over a long time, natural

selection can lead to change Helpful variations may accumulate in a species,

while unfavorable ones may disappear

Environmental ChangeWhen copper contaminated the soil surrounding the monkey flowers, the environment changed. What do you think the area will look like in ten years?

Natural Selection

Natural Selection

What is natural selection? Genes and natural selection – Without

variations, all members of a species would have the same traits and same chance of surviving and reproducing

Variations can result from changes in genes Only traits that are inherited, or controlled by

genes, can be affected by natural selection

Natural Selection

Natural Selection

Evolution of Man Years back to common ancestor of humans and *

All humans – about 140,000 years ago Chimpanzees – about 6 mya Gorillas – about 7 mya Orang utans – about 14 mya Gibbons – 18 mya Old World monkeys – 25 mya New World monkeys – 40 mya

* From “The Ancestor’s Tale – A Pilgrimage to the Dawn of Life”

Richard Dawkins, 2004 by Weidenfeld & Nicolson

Natural Selection

Evolution of Man Years back to common ancestor of humans and

Rodents and rabbitkind – 75 mya Monotremes – 180 mya Birds – 310 mya Sponges – 800 mya Plants - 3600 mya

Natural Selection Classwork

1. How do life forms change over time?

2. How does genetic variation contribute to the diversity of organisms?

3. How long ago did the common ancestor of all humans live?

4. How long ago did the common ancestor of humans and chimpanzees live?

5. How long ago did the common ancestor of humans and rodents live?

Biodiversity and Extinction

What is biodiversity? The number of different species in an area is its

biodiversity

Biodiversity and Extinction

What factors affect biodiversity? Area – a large area will support more species than a small

one Climate – areas with more rainfall and higher temperatures

have more biodiversity than those with less rainfall and lower temperatures

Diversity – diverse traits exist in individuals in a healthy population (example: color, size). These organisms have genes that are shared and genes that are different

Niche diversity – a niche is the role that an organism plays in its habitat. Diverse ecosystems have more niches

The map shows the ranges of Kaibab and Abert’s squirrels.

Biodiversity and Extinction

Park SizeThe dark green area represents three different park plans. Which plan supports the most bio-diversity?

Biodiversity and Extinction

Biodiversity and Extinction

Differences in Biodiversity

Biodiversity tends to increase as you move toward the equator because temperatures tend to be warmer.

Number of mammal species in each country

Biodiversity and Extinction

Differences in Biodiversity Ecosystems with the highest biodiversity usually

have warm, moist climates. In fact, tropical regions contain two-thirds of all

of Earth's land species. Costa Rica is a tropical Central American country

about the size of West Virginia. Yet it is home to as many bird species as there are in

the United States and Canada combined. In addition, there are biodiversity hot-spots that

do not depend on latitude

Biodiversity and Extinction

Why is biodiversity important? For people, it provides food, medicines, and

many products. Furniture and buildings are made from wood and

bamboo. Fibers made from cotton, flax, and wool are

woven into clothing. Every species on Earth plays a certain role and

is necessary in the cycling of matter. As a result of biodiversity, soils are richer,

pollutants break down, and climates are stable.

Biodiversity and ExtinctionHumans Need Biodiversity Biodiversity can help improve food crops.

Crossbreeding a small population of Mexican wild corn with the US corn crop yielded a strain of corn resistant to a new fungal disease

Biodiversity strengthens an ecosystem.

In a vineyard, vines grow close together, and a disease infecting one grapevine could easily move to another plant, infecting the entire vineyard.

Planting alternate rows of different crops can help prevent disease and reduce or eliminate the need for pesticides.

Biodiversity and Extinction Humans Need Biodiversity

Medicines Most medicines used today originally came

from wild plants Scientists still are discovering new species. The next plant species discovered could be

the cure for cancer.

Pacific Yew

Source of drug taxol used to treat ovarian cancer

Biodiversity and Extinction

Extinct species a species that was once present on Earth but

has died out.

Endangered species a species in danger of becoming extinct

Threatened species a species is likely to become endangered in

the near future

Biodiversity and Extinction

Why do species go extinct? Once the population of a species drops below a

certain point, it may not be able to recover One way that this can happen is if a species

becomes isolated, cut off geographically from others of its species

Another way is habitat loss, when land area available for a species to live decreases due to human activity

Biodiversity and Extinction

Factors affecting biodiversity Native and non native species

Native species are the original organisms in an ecosystem.

An introduced (non-native) species is one that moves into an ecosystem as a result of human actions. They often have no competitors or predators in the new

area, so their populations grow rapidly. They become invasive species when they crowd out or

consume native species.

Biodiversity and Extinction

Factors affecting biodiversity Native and non native species

Competition Non-native species compete for the same resources

(food, water, air, nesting sights, etc.) as native species

Limited resources Non-native species may use up scarce resources which

will then not be available for native species.

Biodiversity and Extinction

Factors affecting biodiversity Non-native species

The Australian pine was introduced in the 1800s for lumber and erosion control. Because it can tolerate saltwater and out competes many native plants, it has taken over.

Biodiversity and Extinction

Factors affecting biodiversity Non-native species

The red lionfish is a venomous invasive species on the east coast of the US and in the Caribbean. It has few natural predators, “high rates of prey consumption, a wide variety of prey, and increasing abundance of the fish”

Sources: Florida Natural History Museum, Wikipedia/wiki/Red_lionfish

Biodiversity and Extinction

Factors affecting biodiversity Non-native species

The Cuban treefrog preys upon smaller native treefrogs and may reduce their populations via competition and predation

Source: Florida Fish and Wildlife Conservation Commission

Biodiversity and Extinction

Factors affecting biodiversity Non-native species

The Burmese python preys upon native species and may reduce their populations locally.

Source: Florida Fish and Wildlife Conservation Commission

Biodiversity and Extinction

Factors affecting biodiversity Habitat loss

When habitats of some species become smaller or disappear completely due to human activity.

Habitat loss may be due to divided habitats, when a habitat is divided by roads, cities, or farms.

May reduce biodiversity.

Biodiversity and Extinction

Factors affecting biodiversity Habitat loss

The Key Largo cotton mouse has become an endangered species. The building of houses, roads, and hotels is reducing the mouse's habitat (and pythons).

Biodiversity and Extinction

Factors affecting biodiversity Habitat loss

The Florida black bear is the only subspecies of black bear living in a subtropical region. Habitat loss and bears being injured or killed by motorists is another threat to regional populations.

Source: Wikipedia/wiki/Florida_black_bear

Biodiversity and Extinction

The Bartram scrub-hairstreak butterfly is endangered because its habitat, the place where it lives, is being destroyed.

One place where this butterfly lives is the Richmond Tract, a pine rockland next to MiamiZoo.

Biodiversity and Extinction

The Florida bonneted bat, also endangered, lives in pine rocklands

The Miami Blue butterfly is endangered because its coastal habitat is being destroyed by development.

Biodiversity and Extinction

The Miami Tiger beetle, also endangered, lives in pine rocklands only in Miami

An endangered plant species, the deltoid spurge, is a pine rockland resident.

Biodiversity and Extinction

The Florida Key Deer is endangered; they live mostly on Big Pine Key.

Biodiversity and Extinction

The Florida Panther’s habitat is being lost and it is endangered.

Biodiversity and Extinction

Slow Down for Panthers!Road signs such as this one warn drivers in Florida to watch out for panthers in the road.

UpdateAs of November 2014, 19 panthers had been killed by cars in

South Florida

Biodiversity and Extinction

Florida PanthersThis pie chart shows the causes of death for Florida panthers between 1997 and 2007.

Mass extinctions – past and present

Over the geologic time of the Earth, there have been five mass extinctions

In a mass extinction, there is a widespread and rapid decrease in the amount of life on Earth

Here is a list of the five and their possible causes

Cretaceous–Paleogene extinction event (K-Pg event; formerly K-T event)

66 mya Likely Cause: Impact event About 17% of all families, 50% of all genera and

75% of all species became extinct. In the seas it reduced the percentage of sessile

animals to about 33%. All non-avian dinosaurs became extinct during that

time Mammals and birds emerged as dominant land

vertebrates in the age of new life.

Triassic–Jurassic extinction event

200 mya Cause: Global warmimg About 23% of all families, 48% of all genera (20% of

marine families and 55% of marine genera) and 70% to 75% of all species went extinct.

Most non-dinosaurian archosaurs, most therapsids, and most of the large amphibians were eliminated, leaving dinosaurs with little terrestrial competition.

Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments.

Permian–Triassic extinction event

251 mya Cause: Massive volcanism? Sea level fall? Global

cooling? Earth's largest extinction killed 57% of all families, 83%

of all genera and 90% to 96% of all species (53% of marine families, 84% of marine genera, about

96% of all marine species and an estimated 70% of land species, including insects).

Ended the primacy of mammal-like reptiles. In the seas, the percentage of animals that were sessile

dropped from 67% to 50%. "Great Dying".

Late Devonian extinction

375 – 360 mya Cause: Sea level fall? Anoxic event? A prolonged series of extinctions eliminated about

19% of all families, 50% of all genera and 70% of all species.

This extinction event lasted perhaps as long as 20 Ma, and there is evidence for a series of extinction pulses within this period.

Ordovician–Silurian extinction event

450–440 Mya Cause: Sea level fall? Global cooling? Anoxic

event? Two events occurred that killed off 27% of all

families, 57% of all genera and 60% to 70% of all species.

Together they are ranked by many scientists as the second largest of the five major extinctions in Earth's history in terms of percentage of genera that went extinct.

Holocene

Ongoing Cause: human activity Sometimes called the Sixth Extinction Proposed to describe the extinction event of species that

has occurred during the present Holocene epoch (since around 10,000 BCE) mainly due to human activity.

The large number of extinctions span numerous families of plants and animals including mammals, birds, amphibians, reptiles and arthropods.

The present rate of extinction may be up to 140,000 species per year.

Biodiversity and Extinction Classwork

1. How do new species form?

2. What factors affect biodiversity?

3. What are the ways in which a species can become extinct?