Life Sciences Term 2

Geological Time Scale

A system used to organize Earth's history into Eons, Eras, Periods, and Epochs based on significant events

Eons

The longest divisions of geological time spanning hundreds of millions of years

Phanerozoic Eon

The most recent eon that began about 500 million years ago

Eras

Subdivisions within eons

Three eras of the Phanerozoic Eon

Paleozoic, Mesozoic, and Cenozoic

Periods

Subdivisions within eras that vary in length

Paleozoic periods

Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian

Earth formed

About 4.6 billion years ago

Earth's crust solidified

About 4 billion years ago

First life appeared in oceans

About 3.5 billion years ago

Oldest micro-organism fossils found

Western Australia

Prokaryotes dominated Earth

From 3.5 billion to 2 billion years ago

Two groups that diverged from prokaryotes

Bacteria and Archaea

Oxygen started accumulating in atmosphere

About 2.5 billion years ago due to cyanobacteria

Oceans contained significant oxygen

About 2 billion years ago

Oldest eukaryotic fossils

About 1.5 billion years ago

First cells with nuclei

Appeared about 1.5 billion years ago

Oldest animal fossils

About 600 million years ago

First multicellular organisms

About 700 million years ago

Cambrian Explosion

Rapid diversification of animal life about 540 million years ago

Colonization of land by plants, fungi, and animals

About 450 million years ago

First land plants with xylem vessels

Appeared about 450 million years ago

Largest mass extinction

About 250 million years ago killing 99% of life

Age of Dinosaurs began

About 250 million years ago

Supercontinent began breaking apart

About 180 million years ago

Dinosaurs became extinct

About 65 million years ago

Percentage of life lost in dinosaur extinction

About 70%

Mammals evolved

About 200 million years ago

First proto-humans

Appeared in Africa about 4 million years ago

First ancestors of Homo sapiens

About 200 000 years ago

Recorded human history began

About 5 000 years ago

Cambrian Explosion definition

A short period where most major animal groups suddenly appeared in the fossil record

Duration of Cambrian Explosion

Lasted about 20 million years

Platyhelminthes

Flatworms

Nematoda

Worms

Annelida

Segmented worms

Mollusca

Slugs, snails, and shelled organisms

Arthropoda

Invertebrates with exoskeletons and jointed limbs

Echinodermata

Marine invertebrates

Chordata

Vertebrates with skeletons

Fish evolved

About 500 million years ago

Amphibians evolved

About 370 million years ago

Reptiles evolved

About 340 million years ago

Birds evolved

About 150 million years ago

Mammals evolved from primitive forms

About 200 million years ago

Humans evolved

About 200 000 years ago

Mass extinction

A period where many species die out in a relatively short time

First mass extinction

Ordovician extinction caused by climate change

Ordovician extinction effect

Extinction of many trilobites

Second mass extinction

Devonian extinction caused by ice ages and global cooling

Third mass extinction

Permian extinction caused mainly by volcanic eruptions

Most severe mass extinction

Permian extinction

Fourth mass extinction

Triassic extinction caused by acid rain and low ocean oxygen

Fifth mass extinction

Cretaceous extinction caused by asteroid impact

Current possible sixth mass extinction

Caused by human activities

Human causes of sixth extinction

Illegal veld fires, habitat destruction, and hunting

Environmental disaster theory

Mass extinctions caused by meteors, volcanism, radiation, or diseases

Failure to adapt theory

Organisms become extinct because they cannot adapt to environmental changes

Fossil

Preserved remains or traces of organisms from long ago

Paleontologist

Scientist who studies fossils

Paleoanthropologist

Scientist who studies human ancestors through fossils

Petrification

Process where organic remains are replaced by minerals and become stone-like

Sedimentary rock

Rock formed from layers of sediment in aquatic environments

Transitional fossil

Fossil showing features of ancestral and descendant groups

Step 1 of fossil formation

Organism buried by sediment

Step 2 of fossil formation

More sediment accumulates and minerals replace organic matter

Step 3 of fossil formation

Tectonic movement lifts sediments closer to surface

Step 4 of fossil formation

Erosion exposes fossils

Relative dating

Estimating fossil age by comparing with other fossils or events

Radiometric dating

Determining exact age using radioactive isotopes

Examples of fossils

Bones, shells, footprints, coprolites, petrified wood, leaf imprints

Coprolites

Hardened fossilized faeces

Examples of fossils preserved in unusual conditions

Woolly mammoths in ice and sabre-toothed cats in tar

Organic molecules

Molecules mainly made of carbon, hydrogen, and oxygen

Inorganic compounds

Compounds that usually do not contain carbon

Micronutrient

Element needed in small amounts

Macronutrient

Element needed in large amounts

Main organic compounds in cells

Carbohydrates, lipids, proteins, nucleic acids, enzymes, and vitamins

Main inorganic compounds in cells

Water and mineral salts

Percentage of water in cells

70-95%

Water as universal solvent

Dissolves many substances for transport and reactions

Water function in plants

Maintains turgidity

Water function in organisms

Removes waste products

Macro-nutrients

Essential minerals needed in large amounts

Micro-nutrients

Essential minerals needed in small amounts

Sodium function in animals

Water-salt balance and nerve and muscle function

Sodium deficiency symptom

Muscular cramps

Potassium function in plants

Forms proteins and enzymes

Potassium function in animals

Water-salt balance and heart, muscle, and nerve function

Potassium deficiency in plants

Slow growth

Potassium deficiency in animals

Muscle weakness and irregular heartbeat

Calcium function in plants

Root development and cell wall formation

Calcium function in animals

Bone and teeth formation and muscle function

Calcium deficiency in plants

Chlorosis

Calcium deficiency in animals

Rickets and weak bones and teeth

Phosphorus function in plants

Root development

Phosphorus function in animals

Bone and teeth formation

Phosphorus deficiency in plants

Brown leaves

Phosphorus deficiency in animals

Bone and teeth weakness, nerve and muscle malfunctioning

Magnesium function in plants

Formation of chlorophyll