Unit 3 Biodiversity Section

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.

Biodiversity Case Study-Siberian Tigers—Loss of habitat and potential biodiversity. Biodiversity looks at the diversity of the species; their genes, their populations, their communities.

Earth is home to a tremendous diversity of species Ecosystem diversity- the variety of ecosystems within a given region. Species diversity- the variety of species in a given ecosystem. Speciation, the generation of a new species; increases biodiversity. Genetic diversity- the variety of genes within a given species.

Which community has a greatest diversity? Biodiversity: the number of different species in a given area – a measure of the health of the environment. 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. Which community has a greatest diversity?

Biodiveristy is unevenly distributed Living things are distributed unevenly across Earth Latitudinal gradient = species richness increases towards the equator

Biodiversity losses and species extinction Extinction = occurs when the last member of a species dies and the species ceases to exist Extirpation = the disappearance of a particular population from a given area, but not the entire species globally Can lead to extinction

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.

Biodiversity Causes Reasons for biodiversity losses are multifaceted, complex, and hard to determine Factors may interact synergistically Four primary causes of population decline are: Habitat alteration-many man-made Invasive species-non native species introduction-Fig 11-13 Pollution-Air, Water… Overharvesting—over hunting… Global climate change now is the fifth cause

Biodiversity provides free ecosystem services Provides food, shelter, fuel Purifies air and water, and detoxifies wastes Stabilizes climate, moderates floods, droughts, wind, temperature Generates and renews soil fertility and cycles nutrients Pollinates plants and controls pests and disease Maintains genetic resources Provides cultural and aesthetic benefits Allows us to adapt to change

Biodiversity generates economic benfits People like to experience protected natural areas, creating economic opportunities for residents, particularly in developing countries Costa Rica: rainforests Australia: Great Barrier Reef Belize: reefs, caves, and rainforests A powerful incentive to preserve natural areas and reduce impacts on the landscape and on native species But, too many visitors to natural areas can degrade the outdoor experience and disturb wildlife

Island Biogeography Equilibrium theory of island biogeography = explains how species come to be distributed among oceanic islands Also applies to “habitat islands” – patches of one habitat type isolated within a “sea” of others Explains how the number of species on an island results from an equilibrium between immigration and extirpation Predicts an island’s species richness based on the island’s size and distance from the mainland

Island Biogeography Fewer species colonize an island far from the mainland Large islands have higher immigration rates Large islands have lower extinction rates

3.1 SPECIALIST AND GENERALIST SPECIES The way species utilize their niches can be broadly grouped as generalists or specialists.

The advantage of specialist species is that competition is reduced. The Giant Panda is an example of a specialist species. It has a narrow niche with no predators except man. The advantage of specialist species is that competition is reduced. However, when food and habitat are limited, survival is threatened due to lack of adaptability. Only about 800 Pandas are alive in the wild and 220 are in zoos. They are more closely related to raccoons than to bears.

The Panda’s habitat is western China where human population is soaring The Panda’s habitat is western China where human population is soaring. It has become endangered because: loss of habitat - people are encroaching specialized diet – Pandas feed only on bamboo and need to spend most of the day eating up to 1/3 of its body weight. Bamboo has a natural tendency to die back and grow slowly.

low birth rate - one cub every other year; at birth the baby is blind, without fur, and weighs only 5 oz. finicky mating habits - Pandas are usually solitary, but during courting the males are very possessive. Mothers must care for their young for 2 years - assuming the mother survives. Adults weigh about 250 lbs.

It became endangered simply from hunting. The American Alligator is an example of a generalist specie that also has no predators except man. It became endangered simply from hunting. When hunting alligators became illegal, the species made a huge comeback.

They showed up in swimming pools, drainage ditches and retention ponds They showed up in swimming pools, drainage ditches and retention ponds. People were even feeding them. Alligators began to consume ducks, hunting dogs, pets, pigs, deer, cattle, wading birds, and people! EPA By 1977, alligators were removed from endangered status to threatened status. Hunting with a permit is now allowed.

Competition from other species is their only disadvantage. The advantage of generalist species is their wide niche and habitat choices. Competition from other species is their only disadvantage. FWS On farms, reproductive rates have increased 4 fold, growth rates have doubled, and unplanned mortality reduced by 34%. Alligator serve a vital role in the ecosystem and are tied to a healthy food web.

Keystone or Foundation Species?

Keystone or Foundation? Pisaster ochraceus is an efficient predator of the common mussel, Mytilus californicus. It reduces abundance of M. californicus, allowing other macroinvertebrates to persist. If Pisaster present = diverse intertidal community. Based on the research of Dr. Robert T. Paine

Dr. Robert T. Paine’s Work (a) The sea star Pisaster ochraceous feeds preferentially on mussels but will consume other invertebrates. With Pisaster (control) Without Pisaster (experimental) Number of species present 5 10 15 20 1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73 (b) When Pisaster was removed from an intertidal zone, mussels eventually took over the rock face and eliminated most other invertebrates and algae. In a control area from which Pisaster was not removed, there was little change in species diversity.

Keystone or Foundation? Removing three species of kangaroo rats changed a desert plain into an arid grassland. In areas without kangaroo rats, grasses filled in between the shrubs, stems and other plant litter accumulated, large-seeded plants replaced those with smaller seeds, snow melted more slowly and the numbers of the other rodents increased significantly. Based on the research of Dr. James H. Brown

Keystone or Foundation? Keystone (engineer) Pdog burrows act as homes to other creatures, including burrowing owls, badgers, rabbits, black-footed ferrets, snakes, salamanders, and insects. Their burrowing activity works to loosen and churn up the soil, increasing its ability to sustain plant life. Their foraging and feeding practices enable a more nutritious, diverse and nitrogen-rich mixture of grasses and forbs (broad- leafed vegetation) to grow.

Keystone or Foundation? Dominant primary producer that provides food and shelter for many other species Kelp

Effects of losing the “keystone” predator… A trophic cascade- in a food web, the cascading effect that a change in the size of one population (usually an apex predator) in the web has on the populations at lower levels. Example: Gray Wolf in Yellowstone National Park (Wolf -> Elk -> Cottonwood/Aspen/Willow --> Bird Populations)

Don’t forget… A keystone species is one that has a disproportionate impact on its ecosystem when compared to its abundance. A foundation species is usually a primary producer that dominates an ecosystem in abundance and influence. Salmon as a Keystone Species

Major Legislation Endangered Species Act (1973) (ESA) = forbids the government and private citizens from taking actions that destroy endangered species or their habitats To prevent extinction Stabilize declining populations Enable populations to recover As of 2007, the U.S. had 1,312 species listed as endangered or threatened

Protecting Biodiversity Captive breeding – individuals are bred and raised with the intent of reintroducing them into the wild Zoos and botanical gardens Some reintroductions are controversial Ranchers opposed the reintroduction of wolves to Yellowstone National Park Some habitat is so fragmented, a species cannot survive Cloning

International Conservation Efforts UN Convention on International Trade in Endangered Species of Wild Fauna and Flora (1973) (CITES) – protects endangered species by banning international transport of their body parts

Biodiversity Hotspots Biodiversity hotspots – prioritizes regions most important globally for biodiversity Support a great number of endemic species = species found nowhere else in the world The area must have at least 1.500 endemic plant species (0.5% of the world total) It must have lost 70% of its habits impact

Biodiversity Hot Spots