History of Life on Earth

Geologic Time Scale

Geologic Time Scale

Shows significant events in the history of Earth and of the evolution of living things

Were able to develop this timescale by studying rock layers and index fossils worldwide which made it possible for them to identify the relative age of Earth.

Relative Age of Earth

4.5 billion Years

3 Ways Archaeologists Tell the Age of Sites and Artifacts

Absolute Dating, Relative Dating, and Radioactive Dating

Absolute Dating

A method that provides a specific calendar year for the occupation of a site.

Relative Dating

A technique that determines the age of an object in relation to other objects without providing a specific date.

Is an estimate whether an object is younger or older than other things found at the site

Radioactive Dating

A method of dating rocks and minerals using radioactive isotopes.

The Levels of Division in the Geologic Time Scale

Eon, Eras, Periods, Epochs

Eon or Eonothem

The largest and longest divisions in the geologic timeline.

Era or Erathem

A smaller division within Eons in the geologic time scale.

Period or Systems

Further subdivisions within Eras.

Epoch or Series

Finer subdivisions within the Cenozoic and some parts of the Mesozoic era.

Phanerozoic Eon

The eon characterized by "Visible Life."

Eras within the Phanerozoic Eon

Cenozoic Era, Mesozoic Era, Paleozoic Era.

Cenozoic Era

The era known as the "Age of Mammals" or "Recent/Modern Life."

Periods within the Cenozoic Era

Quaternary Period, Neogene Period, Paleogene Period

Quaternary Period

The period marked by the "Rise of Man."

Epochs within the Quaternary Period

Holocene and Pleiostocene

Holocene Epoch

Known as the Recent Epoch and includes historical time.

Pleistocene Epoch

The epoch associated with ice ages and the origin of Homo.

Neogene Period

Known as the Upper/Later Tertiary

Epochs within the Neogene Period

Pliocene and Miocene

Pliocene Epoch

Bipedal humans appear

Miocene Epoch

Mammals and Angiosperms continue to diversify in this epoch

Paleogene Period

Known as the Earlier Tertiary

Epochs within the Paleogene Period

Oligocene, Eocene, and Paleocene

Oligocene Epoch

The origin of the primates

Eocene Epoch

Angiosperms dominate and mammals diversify

Paleocene Epoch

When mammals, birds, and insects diversified

Mesozoic Era

Known as the era of Middle Life.

Was the time of the dinosaurs and the age of reptiles

Was also when Pangaea started to break apart

Periods within the Mesozoic Era

Cretaceous, Jurassic, and Triassic

Cretaceous Period

When angiosperms diversify and dinosaurs were extinct

Jurassic Period

When dinosaurs were abundant, the first birds appeared, and gymnosperms dominated

Triassic Period

When dinosaurs evolved, the origin of mammals, and gymnosperms dominated.

Paleozoic Era

The era known as "Ancient Life"

Periods within the Paleozoic Era

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

Permian Period

Known as the “First Reptiles”

When reptiles diversified and when a major extinction of many marine organisms occurred.

Carboniferous Period

When the first seed plants appeared, the origin of reptiles, and amphibians dominated.

The Two Parts of the Carboniferous Period

Pennsylvanian and Missisipian

Pennsylvanian

The first insects

Missisipian

The Crinoids/ Marine animals

Devonian Period

Known as the Age of Fishes

When bony fishes diversified also when Insects and First Amphibians appeared

Silurian Period

Known as the period of the First Land Plants

Was when the first vascular plants appeared

Ordovician Period

Known as the Age of Invertebrates

When fungi, plants, and animals colonized land

Cambrian Explosion/ Cambrian Period

Marks an important point in the history of life on Earth

A significant event marking the appearance of major animal groups in the fossil record.

The Pre-Cambrian Times and it’s Eons

Is 88% of Earth’s Geologic Time

Contained the Protozoic, Archaean, and Hadean Eon

Protozoic Eon

The longest geologic eon, encompassing the Ediacaran period.

Ediacaran Period

Contained the appearance of Algae and Invertebrates

when the oldest fossils of eukaryotic cells are dated

Carbonate rocks are abundant

Archaean Eon

Known as the earliest period in the geologic period

When atmospheric oxygen concentration increases

Contained the oldest fossils of cells and oldest known rocks

Cynobacteria

The oldest fossils of cells

Acasta Gneiss

The oldest known rocks

The Hadean Eon

Known as the Oldest Eon

Had Earthworms

Ka / Kilo annum

Is a thousand years

Ma / Mega annum

Is a million years

Ga / Giga annum

Is a billion years

Natural Selection

The process by which individuals with characteristics not suited to the environment will die off, whereas those with characteristics will pass these on to their offspring

Produces organisms with improved body structures for their habitats.

Concept of Fitness

The central process of evolution by natural selection

Fitness

An individual's ability to survive and reproduce in a specific environment.

Example of Environmental Pressures in Natural Selection

Overpopulation, Resource Competition, Changing Environments, Predators

Principle of Descent with Modification

The concept that present-day organisms are different from their ancestors.

Raphus cucullatus/Dodo bird

Found in Mauritius in the Indian Ocean, East Madagascar.

Had been nonflying and overweight allegedly unfit to their environment since this made them easy prey

Obesity, slowness, and lack of intelligence are cited as reasons for their extinction

Stabilizing Selection

When an average phenotype is favoured compared to extreme phenotypes

Ex. Robins lay 4 eggs because if they lay more they lack resources however if they lay less some will not hatch.

Directional Selection

A type of natural selection that favors one extreme phenotype over others.

A change in the environment shifts the spectrum of phenotypes observed

Ex. Big seeds are common so birds with bigger beaks will survive better.

Ex. Giraffe’s Neck

Diversifying/Disruptive Selection

A type of natural selection that favors two or more extreme phenotypes, while the average phenotype is selected against

Artificial Selection

The process by which humans select variations in organisms for desirable traits. Is done through selective breeding.

Selective Breeding

The practice of choosing parents with specific characteristics to produce offspring with those traits.

Breeders are able to produce a wide range of plants and animals that look very different from their ancestors.

Non-Random Mating

Contributes to the population change from one generation to the next

Is the selected probability of mating with another individual in a population

Inbreeding

A form of Non-random mating.

Is the mating between close relatives more often than distant relatives.

Close Breeding

Is when animals are very closely related and can be traced back to more than one common ancestor

Outbreeding

Also known as Assertive mating

Is a form of non-random mating wherein individuals select distant relatives for mating over close relatives.

Crossbreeding

Is a form of outbreeding when two different animals of two different breeds mate

Hybrid Vigor

The superior traits observed in crossbred progeny.

Grading Up

The process of mating indigenous breeds with improved pure breeds to enhance traits over generations.

Genetic Drift

Caused by unpredictable changes in allele frequencies due to small population sizes

Mutation

The change in the structure of a gene by alterations in the DNA sequence of an organism

Different types of mutations bases on the mechanism done to the DNA molecule

Ex. Pigment pattern

Substitution

Occurs when genetic codon has one altered nitrogenous base.

Insertion

Characterized by the addition of an extra set of base pairs of genetic material

Deletion

When a set of base pairs in the genetic material is omitted

Frameshift

When the information is no longer parsed correctly, resulting in the production of useless proteins.

Recombination

A process by which pieces of DNA are broken and recombined to produce new combinations of alleles. 

Creates genetic diversity at the level of genes that reflects differences in the DNA sequence of different organisms.

Not the major cause of evolution but is a contributing factor

Gene Pool

The combination of all the genes present in a reproducing population or species

A large gene pool has extensive genomic diversity and is better able to withstand environmental challenges.

Gene Flow (Migration)

Happens when there is transfer of genes from the gene pool of one population to another.

Emigration

When organisms leave their habitat

Immigration

Organisms enter and live in another habitat