Estimates whether an object is younger or older than other things found at the site. Relative dating does not offer specific dates, it simply allows to determine if one artifact, fossil, or stratigraphic layer is older than another.
ABSOLUTEDATING
Provide more specific origin dates and time ranges, such as an age range in years. How specific these dates can be will depend on what method is used.
The geologic time scale is the "calendar" for events in Earth history. It is divided into named units of abstract time called - eons, eras, periods, and epochs.
The three main era of time of Earth's history from oldest to youngest
Paleozoic Era
Mesozoic Era
Cenozoic Era
The Phanerozoic Eon started from 543 million years ago to present.
The three eras of the Phanerozoic Eon
Paleozoic Era
Mesozoic Era
Cenozoic Era
Paleozoic Era
Known as the "OLD LIFE", started from 542 mya and lasted for 251 mya
Subdivided into six periods: Permian, Carboniferous, Devonian, Silurian, Ordovician, Cambrian
Ordovician Period (490 to 443 mya)
Fungi, plants, and animals colonizes the land
Silurian Period (443 to 416 mya)
First vascular plants appeared
Devonian Period (416 to 360 mya)
Bony fishes diversified, insect and first amphibians appeared
Carboniferous Period (360 to 299 mya)
1. Firstseed plants appear
2. Origin of reptiles and amphibians dominate
Permian Period (299 to 251 mya)
1. Reptiles diversify
2. Major extinction of marine organism
3. About 96 percent of all marine species
4. Three of every four species on land died out
Mesozoic Era
Started from 248 mya and lasted for 65 mya
Subdivided into three periods: Triassic period, Jurassic period, Cretaceous period
Triassic Period (251 to 200 mya)
Dinosaurs evolve, origin of mammals, and gymnosperms dominate
Jurassic Period (200 to 145 mya)
Dinosaurs abundant, first birds appear, gymnosperms dominate
Cretaceous Period (145 to 65 mya)
1. Angiosperms diversify
2. Dinosaurs extinct at the end of this period
Cenozoic Era
Quaternary Period (2.6 mya - Present)
Pleistocene epoch: Ice ages and origin of Homo
Holocene epoch: The time since the end of the last major glacial epoch, or "ice age", the current time we are living in
Mass Extinction
A short period of geological time in which a high percentage of biodiversity, or distinct species - bacteria, fungi, plants, mammals, birds, reptiles, amphibians, fish, invertebrates - dies out
Charles Robert Darwin is the Father of Evolution
Fossil Records
The most direct evidences that evolution had occurred
The fossil record shows that early evolution of cetaceans (whales, porpoises, and dolphins), which were documented to have lived 50 to 60 million years ago
Fossils found in Pakistan, Egypt, and North America showing the transition from terrestrial to aquatic life
Fossil records have shown how cetacean evolution had resulted to the loss of hind limbs and the development of cetaceans
Transitional feature
A fossil that shows an intermediate state between an ancestral trait and that of its later descendants
A number of fossils of whale ancestors have been discovered in countries such as Pakistan, Egypt, and North America
Biogeography
The discipline of biology that studies the present and past distribution patterns of biological diversity and their underlying environmental and historical causes
Biogeography
The study of how and why organisms live where they do
Organisms differ from one another in a number of traits, but they share basic similarities because they all evolved from a common ancestor
Comparative Anatomy
An important tool that helps determine evolutionary relationships between organisms and whether or not they share common ancestors
Homologous Structure
Similar physical features in organisms that share a common ancestor, but the features serve completely different functions
Analogous Structure
Similar physical features and functions in organisms that do not share a common ancestor
Although the limbs of crocodiles, birds, whales, horses, bats and humans all look very different they share the same five fingered bone structure. This provides evidence for the theory of evolution
Embryonic Development
Organisms that are closely related may also have physical similarities before they are even born
During vertebrate development, all embryos exactly look the same during the very early stages of development
Comparative Embryology
Reveals anatomical homologies not visible in adult organisms
Vestigial Structures
Organs, tissues or cells in a body which are no more functional the way they were in their ancestral form of the trait
Authentication of evolution and hence, were helpful in explaining adaptation
The appendix is not a vestigial organ
Wisdom teeth are considered a vestigial organ -- no longer useful -- because our diet has evolved
The coccyx currently serves as an anchor for muscles; that wasn't its original purpose, so that's why it's considered vestigial
Evidence from Molecular Biology
Closely related species will be more similar to one another than their more distantly related species
Molecular similarities provide evidence for the shared ancestry of life
DNA sequence comparisons can show how different species are related
Comparing the human genetic code with that of other organisms will show that chimpanzee and baboons are human's closest relations