BIO Flashcards
- A system used by scientists to describe timing and relationships in Earth’s history
- Covers from the formation of the planet (4.6B years ago) until today
Geologic Time Scale
Largest interval of the geologic time scale
Eons
4 sub eons
Hadean, Archean, Proterozoic, Phanerozoic
- Formation to 4B years ago
- Intense volcanic activity and frequent meteor attacks
- Cooling and solidifying of the Earth’s crust
- No life known yet
Hadean
- 4 to 2.5B years ago
- Time of early life on Earth and micro organisms started to appear
- First eukaryotes, single celled Algae (1.4B years ago)
- Anaerobic prokaryotes-bacteria and archeans (3.5B years ago)
- Oxygen levels rised due to photosynthetic organisms
Archean
- 2.5B to 541M years ago
- Time of evolution of early life forms and formation of continents
- Appearance of multi-celled organisms
- Eg. Sponges, colonial algae and soft-bodied invertebrates
Proterozoic
- 541M years to present
- Evolution of multicellular life forms and development of first animals
- Includes Paleozoic, Mesozoic and Cenozoic
Phanerozoic
3 eras
Paleozoic, Mesozoic and Cenozoic
Period that spans from tens to hundreds of millions of years
Era
- 541M to 252M years ago
- Rise of the first fish and the land plants
- Time of great diversification
- Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian
Paleozoic
- 252M to 66M years ago
- Meaning middle life
- Time of the dinosaurs
- Triassic, Jurassic, Cretaceous
Mesozoic
- 66M years ago to present
- Evolution of modern mammals and rise of humans
- Paleogene, Neogene, Quaternary
Cenozoic
Spans no more than one hundred million years
Periods
- Smallest division of the geologic time scale
- Characterized by distinctive organisms
Epoch
Lasted from about 66m to 56m years ago
Paleocene Epoch
- 55.8M to 38.9M years ago
- Oldest known fossils of the modern mammals appear here and they were all small weighing less than 10kg
Eocene Epoch
- 33.9M to 23M years ago
- Appearance of the first elephants with trunks, early horses and grasses
Oligocene Epoch
- 23.03M to 5M years ago
- Warmer global climates
- First appearance of Kelp Forests and Grasslands
- Expansion of grasslands is correlated to drying of continental interiors
Miocene Epoch
- 5.3M to 2.6M years ago
- Time of global cooling
- Cooling and drying of the global environment lead to the enormous spread of grasslands and savannas
- Major change in vegetation
- Rise of long legged grazers
Pliocene Epoch
- 2.6m to 11,700 years ago
- Extremely close to modern ones
- Species of Pleistocenes conifers, mosses, flowering plants, insects, mollusks, birds, mammals and others survive up to this day
Pleistocene Epoch
- 11,700 to present day
- The time since the last major glacial epoch or “ice age”
- Small-scale climate shifts
- Little Ice Age - 1200 and 1700 A.D
- Age of Humans
Holocene Epoch
is the gradual process of change that transformed life on Earth. It refers to descent with modification.
Evolution
- process through which population of living organisms adapts and change
- The Struggle for Existence-members of each species have to compete for food, shelter, other life necessities Survival of the Fittest-Some individuals better suited for the environment
Natural selection
nature provides the variation among different organisms, and humans select those variations they find useful.
Artificial Selection