1. Causes of Species Endangerment
Topic 40

2. What is a Species?
capable of interbreeding with one another in the wild (and produce viable offspring) but do not interbreed with other organisms
about 2 million species have been named and described BUT …

3. Why Do We Need High Biodiversity?
4 main reasons:
genetic reserves
genetic engineering
medicinal, agricultural, and industrial purposes
aesthetic, ethical, and spiritual value

4. Genetic Reserves
maintenance of a broad genetic base is critical for species’ long-term health and survival
e.g. genetically uniform crops eventually lead to increased susceptibility to pests and disease
we can avoid this problem by crossing crops with more genetically diverse ancestral relatives

5. Genetic Engineering
the incorporation of genes from one organism into an entirely different species
helps us obtain new vaccines, more productive farm animals, and longer lasting agricultural products

6. Medicines, Agriculture, and Industry
the 20 best-selling prescription drugs in the U.S. are either natural products or manufactured drugs that were originally obtained from organisms
ultimate sources of food, clothing, and shelter

7. Extinct Species
extinction: the death of a species; occurs when the last individual member of a species dies
irreversible and inevitable

8. Background vs. Mass Extinctions
background extinction: continuous, low-level extinction of species
mass extinction: periods in Earth’s history when numerous species disappeared during a relatively short period of geologic time
episodes may have lasted millions of years
caused by:
major climate changes
catastrophes

9. Present-Day Extinctions
even though extinction is a natural process, it can be accelerated by human activity
one of the main causes of recent extinctions is habitat destruction
extinctions are currently occurring at 100-1,000x the natural rate of background extinction

10. Endangered and Threatened Species
endangered species (legal definition): a species in imminent danger of extinction throughout all or a significant portion of its range
threatened species: when extinction is less imminent but the population of a particular species is quite low (likely to become endangered in the foreseeable future)

11. Characteristics of Endangered Species
species are vulnerable to extinction when they:

12. … Have a Localized Range
some species have an extremely small (localized) range (conditions in which they are physically capable of living)
extinction can occur if the habitat is altered

13. … Have a Large Territory Requirement
extinction can occur if habitat is reduced
e.g. California condor

14. … Live on an “Island”
endemic species: species that are not found anywhere else in the world
populations cannot be replaced by immigration
evolved in isolation  why is this a problem?
can also refer to species in any isolated habitat that is surrounded by an expanse of unsuitable territory
habitat fragmentation: the breakup of large areas of habitat into small, isolated patches (“islands”)

15. … Have Low Reproductive Success
some species have low reproductive success as a result of a small population size or low reproductive rates

16. … Have Specialized Breeding Areas
if a species needs a specific area for breeding, that species is dependent on the habitat being there

17. … Have Specialized Feeding Habits
if a species needs a type of food, the food source and the habitat need to be available

18. K-selected species tend to be susceptible
Large, few in number, long-lived, and have few young

19. Declining Biodiversity
in the U.S., declines are most noticeable in Hawaii, Florida, and California – why?
worst declines:
tropical rainforests (South and Central America, central Africa, and Southeast Asia)
7% of Earth’s land contains ~50% of Earth’s species

20. Biodiversity Loss in Rainforests
1% of rainforest is cleared/degraded every year  leads to species endangerment and/or extinction
many species are endemic
may affect species in other areas (e.g. migrating birds)
clearing changes climate  fewer trees means less rain
many organisms may not be able to tolerate new conditions

21. Biodiversity Loss in Rainforest cont.
loss/degradation of rainforest may affect the evolutionary process
adaptive radiation: the evolution of a large number of related species from an ancestral organism
rainforest clearing reduces nature’s ability to replace its species
countries where rainforest exists are usually the least equipped to protect them – why?

22. Biodiversity Hotspots
relatively small areas of land
high number of endemic species AND are at high risk from human activities
about 25 identified  where?
should we protect just these or focus on ALL biomes?
Most are tropical/many are islands

23. Location of Biodiversity Hotspots

24. Human Causes of Species Endangerment
causes include:

25. … Loss of Habitat
* The single greatest cause of endangerment is LOSS OF HABITAT *
construction, agriculture, logging, mining, or outdoor recreation

26. … Biotic Pollution
the introduction of a foreign species into an ecosystem in which it did not evolve (aka exotic introduction)
invasive species: the foreign species whose introduction causes economic or environmental harm
often upset balance of area
may compete with or prey upon natives
typically caused by humans
islands- particularly susceptible

27. … Environmental Pollution
acid deposition, ozone depletion, and global warming affect ALL habitats

28. … Overexploitation deliberate efforts at eradication or control
e.g. ranchers shooting wolves to protect livestock; prairie dogs being poisoned to prevent them from eating grass
overhunting
strictly controlled in many countries now
e.g. U.S. Army killing bison to disrupt Native Americans/hunters killing them for their tongues

29. Overexploitation continued
poaching =
many animals killed for their furs, horns, skins, etc.
black market
commercial harvest: the collection of a live organism from nature
organisms end up in zoos, aquaria, circuses, pet stores, etc.
many organisms (especially birds) die in transit or from improper treatment
endangered species sold to collectors

30. The Ugliness of Poaching

31. A Note on Frogs and Other Amphibians
Bellwether species (sentinel species/indicator species): provide an early warning of environmental damage that has the potential to affect other species
frogs/amphibians have been declining all over the world – why?
agricultural chemicals, such as pesticides
UV radiation caused by ozone thinning  affects egg survival
infectious diseases
global warming  reduced moisture levels

32. Frogs and Amphibians continued
high percentages of several kinds of deformities
extra legs and toes, eyes located on the shoulder or back, deformed jaws, bent spines, missing extremities and eyes
can be caused by pesticides, parasites, high UV, or a combination of these factors