Causes of Extinction

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Noel Thomas
5 years ago
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Causes of Extinction Extinction the process through which a species disappears from Earth, when

When a species becomes extinct, it no longer exists, which can affect entire ecosystems.

Other species that competed with the extinct species may instead thrive.

1 Causes of Extinction Extinction the process through which a species disappears from Earth, when the birth rate is less than the death rate. When a species becomes extinct, it no longer exists, which can affect entire ecosystems. Species that depended on the now extinct species for food can decline or disappear. Other species that competed with the extinct species may instead thrive. Extinction is a natural part of evolution. Some scientists estimate that 99.9% of all species that ever lived on Earth have become extinct. An average species survives for 2 to 10 million years. 1

Extinctions can occur following a sudden, drastic change in the environment so that species living in the affected area may not be able to adapt quickly enough to survive.

2 Extinctions can occur following a sudden, drastic change in the environment so that species living in the affected area may not be able to adapt quickly enough to survive. If organisms can't adapt or find a new place to live, they die. Most extinctions occur as background extinctions, occurring throughout time. These extinctions are not caused by major catastrophes or horrendous climactic changes, but by small changes in climate or habitat, depleted resources, competition, and other changes that require adaptation and flexibility. Natural events that can cause the extinction of a species: changes in temperature changes in rainfall flooding or drought change in food supply a new predator or disease a volcanic eruption an earthquake shifting land or sea 2

A mass extinction occurs when a large number of species die out all over the world in a fairly short period of time (a few million years is very short in terms of geological time).

Scientists find evidence of mass extinctions in rock layers. At the point of a mass extinction, abundant fossils in the rocks suddenly disappear (a dead zone).

3 A mass extinction occurs when a large number of species die out all over the world in a fairly short period of time (a few million years is very short in terms of geological time). Mass extinctions have occurred many times during Earth's history. During each of these times, more than 50% of all species living at the time died out. Scientists find evidence of mass extinctions in rock layers. At the point of a mass extinction, abundant fossils in the rocks suddenly disappear (a dead zone). Some of these species slowly reappear later, but the fossils of many new species also begin to appear in the rock layers. The five largest mass extinctions in Earth's history: The late Ordovician period (about 438 million years ago) 100 families extinct. The late Devonian (about 360 mya) 30% of animal families extinct. The end of the Permian period (about 245 mya) Trilobites, 50% of all animal families, 95% of all marine species, and many trees die out. The late Triassic (208 mya) 35% of all animal families die out. Most early dinosaur families went extinct. The Cretaceous Tertiary (K T) boundary (about 65 mya) about half of all life forms died out, including the dinosaurs, pterosaurs, plesiosaurs, mosasaurs, ammonites, many families of fishes, clams, snails, sponges, sea urchins, and others. 3

of iridium in the K T rock layer, is that an asteroid 4 9 miles wide hit the Earth about 65 million years ago.

4 The mass extinction where the dinosaurs disappeared was probably caused by the cooling of Earth's climate and a decrease in photosynthesis. Possible reasons for the global climate change: 1) THE ASTEROID IMPACT THEORY (proposed in 1980 by physicist Luis Alvarez and his son Walter Alvarez, a geologist) Their theory, based on teh presence of iridium in the K T rock layer, is that an asteroid 4 9 miles wide hit the Earth about 65 million years ago. The impact would have penetrated the Earth's crust, scattering dust and debris into the atmosphere, and causing huge fires from hot debris thrown from the crater, tsunamis, severe storms, earthquakes, and possibly volcanic activity. The impact could have caused chemical changes in the atmosphere, increasing concentrations of sulfuric and nitric acid, causing acid rain. 2) THE GRADUAL THEORY The movement of tectonic plates and an increase in volcanic activity could also cause global climate change. Volcano eruptions would send thick clouds of dust and soot into the atmosphere. Sulfuric acid from the volcanoes would also lead to acid rain. Lava from the volcanoes could be responsible for the high concentration of iridium in the K T layer. Dust and debris in the atmosphere caused by either a meteor, volcanoes, or a combination of the two would have blocked most of the sunlight for months, lowered the temperature globally, and caused plants to die. Earth's oxygen levels may also have decreased. Major changes in the food chain would result from all of these environmental changes. 4

Mass Extinctions and New Species After the mass extinction of the dinosaurs, a new age of mammals began. As old species disappeared, more resources such as food and shelter became available.

5 Mass Extinctions and New Species After the mass extinction of the dinosaurs, a new age of mammals began. As old species disappeared, more resources such as food and shelter became available. The surviving species may have taken advantage of the resources and increased in numbers. New species may also evolve as adaptations allow populations to take advantage of the resources. Some scientists argue that dinosaurs didn't actually go extinct but evolved into birds. Flying dinosaurs called pterosaurs had skin that stretched between their fingers and bodies to form wings. Archaeopteryx, considered to be the first bird, is thought to be descended from running dinosaurs called theropods. Although extinctions are a natural process, the rate of extinctions of plant and animal species is increasing, due to human activity. Threat Description Remedy Habitat Destruction Invaders Species lose natural homelands, or habitat changes too quickly for survival Land management and preservation, reduce human encroachment Non native species introduced drive Reduce species introduction, out local species through competition, reintroduce and protect native predators, or disease species Pollution Contaminated air, land, or water Reduce pollution Overgrazing, overlogging, forest burning Overharvesting Climate change Poaching, overhunting, overfishing Habitat changed or destroyed Land use management Too many members of a species taken Species management, reduce for food, energy, medicine, etc. demand for products Human actions create ozone depletion, greenhouse effect, etc. Humans cause rapid death of too many individuals in the species Reduce use of climatechanging products Reduce demand for species 5

Warm Up Name the 5 different types of fossils

Warm Up Name the 5 different types of fossils Timeline that organizes the events in Earths history. Earth is about 4.7 billion years old. More complex organism such as land plants and fish evolved only