MASS EXTINCTION, the role in evolution, and the types of mass extinction

mass extinction , the role in evolution, and the types of mass extinction

1. MASS EXTINCTION Savidha sam Msc I zoology St Gregorios College

2. MASS EXTINCTION A mass extinction or extinction event refers to an abrupt decrease in the number of species in a short span of geological time. The term is different from simple extinction that denotes in ecology the disappearance of an organism or group of taxa. While extinctions are quite common in nature, mass extinctions are relatively rare events.

3. CAUSES OF MASS EXTINCTIONS

4. FIVE MASS EXTINCTIONS are Ordovician-Silurian Extinction Late Devonian Extinction Permian-Triassic Extinction Triassic-Jurassic Extinction Cretaceous-Tertiary Extinction

5. Ordovician-Silurian Extinction - 444 million years ago During this extinction, the life of small aquatic organisms ended. This happened 440 million years ago. 60% of the animal species got extinct during this period The event took its hardest toll on marine organisms such as corals, shelled brachiopods, eel-like creatures called conodonts , and the trilobites.

6. Late Devonian extinction - 383-359 million years ago eliminated about 19% of all families 50% of all genera and at least 70% of all species. Many tropical marine species went extinct The extinction seems to have only affected marine life. Hard-hit groups include brachiopods, trilobites, and reef-building organisms; the reef-building organisms almost completely disappeared.

7. The largest mass extinction event in Earth's history affected a range of species, including many vertebrates. The Permian–Triassic (P– Tr ) extinction event, sometimes informally called the Great Dying, It killed 57% of all families, 83% of all genera and 90% to 96% of all species Permian-Triassic is the only one that wiped out large numbers of insect species

8. Triassic-Jurassic Extinction 210 million years ago Triassic–Jurassic ( Tr -J) extinction event , often called the end-Triassic extinction. About 23% of all families, 48% of all genera and 70% to 75% of all species became extinct. Extinction of other vertebrate species on land allowed dinosaurs to flourish

9. CRETACEOUS-TERTIARY EXTINCTION 66 MILLION YEAR AGO About 17% of all families, 50% of all genera and 75% of all species became extinct. This major extinction that wiped out non avian dinosaurs referred as the K-T extinction by Scientists because it happened at the end of the Cretaceous period and the beginning of the Tertiary period. Geologists use "K" for Cretaceous since "C" is used for an earlier period,

10. K-T Extinction Sixty-six million years ago, more than three-fourths of all plant and animal species living on Earth became extinct. This event is known as the K-T mass extinction because it occurred at the boundary between the Cretaceous (K) and Tertiary (T) time periods. The K–T extinction was characterized by the elimination of many lines of animals. Most of them were important elements of the Mesozoic Era (252.2 million to 66 million years ago). Those mainly include nearly all of the dinosaurs and many marine invertebrate

11. EXTINCTION TODAY Earth is currently experiencing a biodiversity crisis. Recent estimates suggest that extinction threatens up to a million species of plants and animals, in large part because of human activities such as deforestation, hunting, and overfishing. Other serious threats include the spread of invasive species and diseases from human trade, as well as pollution and human-caused climate change .

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