EXTINCTION IN THE MODERN WORLD CHAPTER 1.3

QUESTION: How can one of the largest population of bird, the passenger pigeon, disappear in only 65 years? ANSWER: HUMANS

HUMANS AND THE RATE OF EXTINCTION Humans have had a profound effect on other organisms. Species extinction rates are increasing dramatically as the human population grows. Between 1600 – 1900 the estimate is that one species went extinct every four years. 21 Century projection is that one species will become extinct every 30 minutes.

HUMANS AND THE RATE OF EXTINCTION Majority of threatened species can be found in tropical rainforests Species at risk extinction is growing, at the rate of about 80 species per year.

BRIEF HISTORY OF EXTINCTION Mass extinctions occurred before humans existed. Scientists believe that most mass extinctions occurred because ASTEROIDS crashed into the Earth. This caused dust particles that blocked the sun for long periods of time causing the sunshine not to reach the surface of the Earth.

MASS EXTINCTIONS 438 Million years ago the first mass extinction of marine organisms took place 360 Million years ago the same thing happened again 245 Million years ago the largest extinction took place destroying 80% of all species. 208 Million years ago a fourth catastrophe occurred and the birth of dinosaurs was created.

MASS EXTINCTIONS The most famous mass extinction occurred 65 million years ago, which marked the end of the dinosaur. ( ICE AGE)ICE AGE There is evidence that an asteroid hit Earth just off the Yucatan Peninsula of Mexico. 9.6 km deep and 300 km wide. ( roughly here to PEI)

OTHER CAUSES OF EXTINCTION CLIMATE CHANGE COMPETITION HUMAN ACTIVITIES Both of these cause species to adapt or die. As a species adapts or dies this has major effects on each ecosystem and food chain.

EFFECTS OF EXTINCTION The number of species in an ecosystem is described as the biological diversity or BIODIVERSITY of the ecosystem. The reduction in biodiversity caused by the extinction of a single species can cause a “domino effect.” When the threatened species acts as a predator, it keeps the population of its prey in check.

EFFECTS OF EXTINCTION When it acts as prey, it provides an important food source. So, An increase in Biodiversity = Healthy ecosystem. A decrease in Biodiversity = greater chance of Ecosystem Collapse.

SEA OTTER EXAMPLE Decrease in the Sea Otter ( predator ) Means an increase in Sea Urchins Means a decrease in Kelp ( form of seaweed) Means a decrease in Fish ( relies on seaweed for habitat and food ) By protecting the Sea Otters caused a increase in Fish which balanced out the food chain and therefore the ecosystem.