History of Life on Earth and Human Evolution

Spontaneous generation

The idea that nonliving material could give rise to living organisms.

Biogenesis

The concept of 'life-from-life'.

Big Bang theory

States that a cosmic explosion occurred billions of years ago, resulting in the formation of clouds of hydrogen and helium atoms.

Reducing atmosphere hypothesis

Proposes that early Earth had an oxygen-poor atmosphere rich in inorganic molecules, leading to the formation of organic molecules.

Extraterrestrial hypothesis

Suggests that organic molecules/life came from other planets.

Deep-sea vent hypothesis

Proposes that key organic molecules originated from deep-sea vents.

Creationism

The belief that humans, life, the Earth, and/or the universe were created by a supreme being or deity's supernatural intervention.

Four overlapping stages hypothesis

A proposed process for the origin of cells, consisting of four stages: formation of nucleotides and amino acids, formation of RNA, DNA, and proteins, molecules being enclosed in membranes, and acquisition of cellular/living properties.

Stage 1 of cell formation

Involves the formation of nucleotides and amino acids prior to the existence of cells.

Stage 2 of cell formation

Involves the formation of RNA, DNA, and proteins.

Stage 3 of cell formation

Involves molecules being enclosed in membranes.

Stage 4 of cell formation

Involves the acquisition of cellular/living properties.

Fossils

Remains or impressions of ancient organisms preserved in geological formations.

Fossil record

Used to help place important events and species in the appropriate geologic era.

Geological timescale

A timeline that describes the timing and relationships of events in Earth's history.

Environmental changes

Types of changes that have affected the history of life on Earth.

Louis Pasteur

Scientist who disproved spontaneous generation in 1862 through pasteurization.

Aristotle

Philosopher who proposed the idea of spontaneous generation.

Cosmic explosion

The event that led to the formation of hydrogen and helium clouds in the Big Bang theory.

Gravitational forces

Forces that collapsed clouds of hydrogen and helium to create stars.

Macromolecules

Large molecules formed from smaller molecules (monomers) during the origin of life.

Water Vapor

Speculated to have supplied atoms of carbon, hydrogen, oxygen, and nitrogen.

Energy Sources for Organic Synthesis

Lightning, heat from volcanoes, and ultraviolet radiation are thought to have provided the energy needed.

Laboratory Reproduction of Experiments

Experiments have been reproduced in the laboratory but cannot prove what actually happened.

Stage 2: Organic Polymers

Simple organic molecules, such as nucleotides and amino acids, became polymerized to form DNA/RNA and proteins.

Clay Minerals

Scientific evidence suggests that organic molecules could polymerize on the surface of clay.

Absence of Enzymes

Polymerization occurred without chemical assistance.

Stage 3: Protobionts

Polymers became enclosed in membranes, forming aggregates of molecules with an outer boundary.

Lipid Bilayer

An outer boundary of protobionts, allowing for the containment of information and catalytic functions.

Self-Replication

Protobionts developed the capability of self-replication.

Liposomes

Vesicles surrounded by a phospholipid layer that could form cell-like structures.

Stage 4: Cellular Properties

Polymers enclosed in membranes acquired characteristics of cells.

RNA as First Macromolecule

Hypothesized to be the first macromolecule found in protobionts.

Chemical Evolution

Once protobionts had genetic material, they could mutate and evolve.

Fossils

Preserved remains of past life on Earth, including bones, shells, and impressions.

Sedimentary Rocks

Fossils are often found in these rocks, formed from particles of older rocks.

Fossil Formation

Most fossils form when organisms are buried quickly, preserving them as sediments pile up.

Paleontologists

Scientists who study fossils.

Relative Ages of Fossils

Determined by their locations within rock layers, with lower layers usually being older.

Radiometric Dating

A method used to estimate the age of fossils.

Geological timescale

A timeline of Earth's history.

Earth formation

Earth was formed about 4.55 billion years ago (bya).

Prokaryotes appearance

Prokaryotes appeared about 3.8-3.5 bya.

Oxygen-producing prokaryotes

Prokaryotes that produce oxygen appeared about 2.4 bya.

Single-celled eukaryotes

Single-celled eukaryotes evolved about 1.8 bya.

Multicellular eukaryotes

Multicellular eukaryotes appeared about 1.5 bya.

First animals

First animals appeared about 632 million years ago (mya).

Plants colonization

About 520 mya, plants started to colonize the land and first invertebrates appeared.

Terrestrial colonization

440 mya - large terrestrial colonization by plants and animals.

Seed plants and insects

400 mya - seed plants and insects first appear.

Reptiles appearance

300 mya - reptiles first appear.

Dinosaurs and mammals

225 mya - dinosaurs and mammals first appear.

Birds appearance

160 mya - birds first appear.

Flowering plants

135 mya - flowering plants first appear.

Apes appearance

7 mya - apes (chimpanzees, gorillas, orangutans, and gibbons) first appear.

Anatomically modern humans

300,000 ya - anatomically modern humans appear.

Environmental changes

Changes that have influenced the types of organisms that have existed during different periods of time.

Extinction

The complete loss of a species or groups of species.

Temperature fluctuations

Temperature changes over time, causing periods that are colder (Ice Ages) and warmer.

Atmospheric changes

Started out with little to no oxygen, then about 2.4 bya, O2 levels began to rise significantly.

Landmasses

Formation of landmasses surrounded by water resulted in two different environments, terrestrial and aquatic.

Floods and glaciations

Events that affect living organisms in the location of these occurrences.

Volcanic eruptions

Can affect living organisms in the vicinity and cause formation of new landmasses, such as islands.

Meteorite impacts

Can affect living organisms in the vicinity and surrounding landmasses and environment, potentially causing mass extinction.

Natural selection

A mechanism that results in evolutionary change, influenced by environmental factors.

Examples of human evolution

Lactose tolerance, blue eye color, and red hair color are examples of traits influenced by natural selection.