Biology

• Geologic Time Scale - Earth's record of the apperance of life-forms.
• Eons - Highest level unit of geologic time scale.
• Hadean - its is the oldest eon and was officially recognizes only in 2012.
• Archean - Still not much clear among geogogist due to the fee fossils or mineral evidence.
• Phanerozoic - spans within the past 541 million years up to the present.
• Phanerozoic - spans within the cambrian explosion.
• Eras - another higest level of geologic time scale.
• Precambrian - long span of time, covering 88 percent of earths life story.
• Paleozoic - Lasted for 300 million years.
• Mesozoic - lasted for 180 million years.
• Cenozoic - began 65 million years ago until present.

  -also known as the "Age of Mammals"
• Periods - ranges from tens of millions of years to less than two million years in length.
• Triassic - began after Earth's worst-ever extinction event devastated life.
• Jurassic - which flourished for 180 million years.
• Cretaceous - 145 million years ago and ended 66 million years ago.
• Archaeopteryx - fossil with a body that looks like a small dinosaur with feathers, has linked birds more related to dinosaurs than to other reptiles.
• Microevolution - pertains to the minor differences in the genetic level between populations of the same species.
• Synthetic Theory of Evolution - combined knowledge of biologist about evolutionary theories with genetics.
• Gene Mutation - can occur in high enough frequencies to impact evolution.

  -can occur in random directions
• Natural Selection - acts on genetic diversity due to these random mutations.
• DNA Mutation - as an agent of Genetic Variation.
• Sexual Selection - plays a role in natural selection and is directly related to courtship and mating behavior.
• Sexual Dimorphism - where females and males exhibit district morphological characteristics.
• Gene Pool - referring to the entire collection of gene and alleles.
• Genetic Drift - Situation when the gene distribution in small population evolve randomly by chance.
• Founder effect - observed when few individuals become seperared from the rest of the population.
• Bottlenect effect - happens when the size of the population is severly reduced.
• Macroevolution - the big changes that can happen in alleles frequencies among population.
• Pattern of Evolution Within the Species Level

  •Gene Flow

  •Speciation
• Physical Separation and Genetic Isolation

  a.Geolographic Isolation

  b.Reproductive Isolation
• Geologic Isolation - such as the presence of mountains, deserts, rivers, of zones of vegetation, can lead species to evolve as food availability or resources may be limited at different locations.
• Reproductive Isolation - instances when species evolved even without any geographical barrier, a condition known as sympatric speciation.
• Mechanical isolation - Some species exhibit differences in the morphological characteristics of their reproductive organs, which can lead to incompatibility in terms of size and shape of the genitalia during maring.
• Gametic isolation - Some species sperm cannot fertilize another species' egg because of a chemical surrounding the egg, which can only be fertilized by binding with chemicals from the same species. When sea urchins, reproduce, they release their gametes into a cloud of sperm and ova that join together to form a microscopic larvae.
• Proterozoic - characterized by the presence of oxygen in the atmosphere due to the emergence of cyanobacteria, allowing other organisms such as eukaryotes and other multicellular organisms.
• Cambrian Explosion - marked by the appearance of many new animal phyla, including mollusks, arthropods, chordates, annelids, and sponges.