A Explain why geographic isolation is important to the process of speciation.


Question Description

The Task:

1. Review the chapter(s) assigned this week.

2. Reflect on one of the following prompts - select only one (1).

AExplain why geographic isolation is important to the process of speciation.
BContrast the two schools of taxonomy: evolutionary systematics and cladistics.

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Mammalian and Primate Evolutionary History The Fossil Record and Geologic Time Biological Evolution  Biological evolution is descent with modification.  This encompasses small-scale evolution   …and large-scale evolution   (changes in gene frequency in a population from one generation to the next) (the descent of different species from a common ancestor over many generations). Evolution helps us to understand the history of life. Early Signs of Life  By 3 billion years ago, large colonies of simple singled-celled organisms, such as blue-green algae, were flourishing at the surface of the oceans and seas.  The most advanced creatures were sponges, which are essentially intermediate between single and multi-celled organisms. The Birth of Earth Biological evolution is not simply a matter of change over time. Lots of things change over time: trees lose their leaves, mountain ranges rise and erode, but they aren’t examples of biological evolution because they don’t involve descent through genetic inheritance. All life shares a common ancestor. The central idea of biological evolution is that all life on Earth shares a common ancestor, just as you and your cousins share a common grandmother. Common Past, Different Paths The shared ancestry of animals with backbones We’re all distant cousins: humans, oak trees, hummingbirds and whales. Through the process of descent with modification, the common ancestor of life on Earth gave rise to the fantastic diversity that we see documented in the fossil record and around us today. Whale Evolution Fossils with transitional features document the transformation of whales Life has a history and different species share common ancestors. The Family Tree  The process of evolution produces a pattern of relationships between species.  As lineages evolve and split and modifications are inherited, their evolutionary paths diverge.  This produces a branching pattern of evolutionary relationships. Phylogeny By studying inherited characteristics and other historical evidence, we can reconstruct evolutionary relationships and represent them on a “family tree,” called a phylogeny. Living Fossils The Horseshoe Crab This phylogeny represents the basic relationships that tie all life on Earth together. When a lineage splits (speciation), it is represented as branching. When a speciation event occurs, a single ancestral lineage gives rise to two or more daughter lineages. Fish With Fingers Vertebrates grew fingers before they left the sea Each lineage has ancestors that are unique and ancestors that are shared. Woolly Mammoths Adaptation of Cold Weather Elephants Clades A grouping that includes a common ancestor and all the descendents (living and extinct) of that ancestor. Reptiles Adaptations and Radiation Trees, Not Ladders Think of phylogenies as branches on a tree, not a ladder. Invertebrates Jellyfish Misconceptions About Humans Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human. Principles of Classification  For example:  Human classification  Kingdom: Animalia  Subkingdom: Metazoan  Phyla: Chordata  Subphyla: Vertebrata  Class: Mammalia Building a Phylogenetic Tree To build a tree biologists collect data about the heritable traits of each organism they are interested in, such as physical characteristics, genetic sequences, and behavioral traits. Taxonomic Concepts  Homologies   Analogies   structures shared through descent from a common ancestor. structures used for the same function that developed independently and are not the result of common descent. Homoplasy  the process by which similarities can develop in different groups of organisms.  An example of homologous characters is the four limbs of tetrapods.  Birds, bats, mice, and crocodiles all have four limbs sharks and bony fish do not. Homologies Not all characters are homologies, in this case the wings are analagies.  Bat wings consist of flaps of skin stretched between the bones of the fingers and arm.  Bird wings consist of feathers extending all along the arm. This phylogeny illustrates how distant bats and birds are in an evolutionary sense. Convergent Evolution Evolutionary adaptation to niches. The Linnaean System of Classification  The classic system of classification was developed by Carolus Linneaus.  In this system every organism is assigned to a kingdom, phylum, class, order, family, genus, and species.  This system is not based on evolution. The Phylogenetic Classification System This system names only clades. Cladistic Taxonomy Groups species according to shared derived characteristics: Primitive traits reflect the ancestral condition. Shared derived characteristics are shared traits that weren’t present before the group's appearance. Genus and Species  Species is the most precise taxonomic level.  Genus is a group of species more closely related to each other than to species from another genus. These Happy Face Spiders all appear different but can interbreed so they are considered the same species. Approaches to the Definition of Species Species are defined by reproductive Biological Species isolation. Only members of the same species can interbreed Concept Recognition Species Concept Key aspect is the ability individuals have to identify members of their own species for mating purposes. Ecological Species Concept A species is a group of organisms exploiting a single niche. Natural selection separates species from one another. Tigons and Ligers Inter-species breeding and viability in offspring. Geologic Time If you wanted to squeeze the 3.5 billion years of the history of life on Earth into a single minute:  Wait about 50 seconds for multi-cellular life to evolve  Wait another 4 seconds for vertebrates to invade the land  Wait another 4 seconds for flowers to evolve  In the last 0.002 seconds “modern” humans arise Complex Multicellular Life The Cambrian Explosion Fossils from the Burgess Shale Dating Techniques  Life began 3.8 billion years ago…  Insects diversified 290 million years ago…  The human and chimpanzee lineages diverged only five million years ago…  How have scientists figured out the dates of long-past evolutionary events? Radiometric Dating The universe is full of naturally occurring radioactive elements. Radioactive atoms are inherently unstable; over time, radioactive “parent atoms” decay into stable “daughter atoms.” This technique relies on the half-life decay of radioactive elements which allow scientists to date rocks and materials directly. Radiometric Dating The principles of radiometric dating and its application in determining the age of Earth Stratigraphy Fossils can be dated relative to one another by noting their positions in layers of rocks, known as strata. This techique provides a sequence of events from which relative dates can be extrapolated. The Permian - Triassic Extinction Event A mass extinction event occurred 250 million years ago Molecular Clocks Some evolutionary changes occur in a clock-like fashion. When a stretch of DNA does indeed behave like a molecular clock, it becomes a powerful tool for estimating the dates of lineagesplitting events. This technique allows scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates. When Dinosaurs Ruled Environment and Adaptation Geologic Time Scale Vast changes have occurred during the life of our planet. There have been cycles of mass extinction, bursts of speciation, and massive geologic changes – even the movement of continents. Deep Time Evolutionary and Geologic History The Insect World Insects and Flowers Ancient Oceans Identifying Fossils Geological Eras  Paleozoic   Mesozoic    The first vertebrates appeared 500 mya Reptiles were dominant land vertebrates. Placental mammals appeared 70 mya Cenozoic  Divided into two periods: Tertiary and Quaternary and 7 epochs: Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene and Holocene. Earth’s Catastrophic Past Continental Drift Plate Tectonics Mammalian Evolution  The Cenozoic era is known as the Age of Mammals.  After dinosaurs became extinct, mammals underwent adaptive radiation, resulting in rapid expansion and diversification.  The neocortex, which controls higher brain functions, comprised the majority of brain volume, resulting in greater ability to learn. Creatures of the Skies Dinosaurs and Birds Major Mammalian Groups  Monotremes   Marsupials   Primitive, egg laying mammals Infants complete development in an eternal pouch Placental  Longer gestation allows the central nervous system to develop more completely Crocodiles 250,000,000 Years Old Bears Adaptation is the Key to Survival Extinction Events  The evolution of life has not been a smooth process.  There have been catastrophic global events such as ice ages, immense volcanic eruptions, and asteroid impacts.  The result has been at least five episodes of mass extinction and many minor ones. Early Primate Evolution  Primate origins began in the placental mammal radiation 65 mya.  The earliest undoubted primates appear in the Eocene epoch.  Most of our knowledge of primate Oligocene evolution comes from a site in Egypt, the Fayum. Mesozoic Insectivore Fayum Forms: Possible Roots of Anthropoid Evolution  Apidium   Small primate that near the evolutionary divergence of Old and New World anthropoids. Aegyptopithecus  Largest of the Fayum primates with a small brain, large snout, and none of the traits of Old World monkeys or hominoids. Miocene Fossil Hominoids  Marked by a spectacular hominoid radiation and could be called “the golden age of hominoids”.  Grouped geographically:  African forms (23-14 mya)  European forms (13-11 mya)  Asian forms (16-7 mya) The location of our very own twig: Humans on the tree of life. The Language of the Body The Human Animal Early hominid lineage gave rise to many other (now extinct) hominids. Humans Who are we - where are we going? ...
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