Evolution Notes Week 2
Evolution Notes Week 2 Anth 314
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This 2 page Class Notes was uploaded by jewellog on Friday October 9, 2015. The Class Notes belongs to Anth 314 at James Madison University taught by Dr. Harlacker in Fall 2015. Since its upload, it has received 16 views. For similar materials see Human Evolution in anthropology, evolution, sphr at James Madison University.
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Date Created: 10/09/15
090815 Thursday September 03 2015 1456 Species and Speciation What is a Species It has been a long and involved question scientists wanted to impose order on what they were observing In general organisms fall into types and the main goal initially was to categorize each animal Biological Species Concept Relies on reproductive isolation A species is a group of natural populations that are capable of interbreeding they can produce fertile offspring Organisms are separate species if they are not capable of interbreeding with each other There are situations in captivity where members of than more than one species will breed tigers and lions tiglon or liger horses and donkeys mules Will there be issue with calling them two different species since they can reproduce YES because this doesn39t happen in the wild Semispecies animals that are members of more than one species Difficult to apply to the fossil record Sometimes the geographical distribution of an animal doesn39t fit this idea because they are all over the place and they may not be reproductively isolated salamander Ecological Species Concept Each species must have its own environmental niche one per species This is okay with their being some genetic exchange between species Sympatric in the same area 0 You may have lots of sympatric groups of monkeys in the rainforest but have different ecological requirements they may have different diets or social systems Also different to apply to the fossil record Debate on whether or not two environments are quotdifferent enoughquot Lice Study Quiz Looking at lice and the way they effect chimps 6 mya humans and gorillas 6 mya They are likely more similar to the last common ancestor we share with each Artie artepithecus she was bipedal she is also very naked and very harry When and why did humanshominins lose their body hair 0 We aren39t entirely sure there are many hypotheses in terms of when having hair was more of a hinderance than it was helpful When and why did humanshominins begin to wear clothing 0 Our first archeological evidence for clothing is in the form of needles or sewing implements 4045000 years ago this would be a minimal age assuming that they wore something before they started sewing o Impressions on clay items of fibers going back 30000 years as well as leather tanning So what can lice tell us about when we lost our body hair andor when we started to wear clothing in comparison with gorillas and chimps Lice are exoparasites they live on the outsides of our bodies they bite and drink our blood they are generally highly specialized one kind of louse only impacts one species Why do we have more variety head lice pubic lice body lice than in those that infect our closest ancestors both chimps and gorillas only have one kind each Are these three different species or are they subspecies of each other how would we determine this 0 Can they breed with each other 0 What are the specifics of their niche drop them into different niches Pubic lice are so different from head and body lice they are commonly seen as a separate species Body Lice some people call them clothing lice 0 Eat less frequently 0 Attracted to areas with other body lice 0 Frequently infest Clothing 0 Tend to return to their preferred habitat when displaced Head Lice 0 Eat more frequently Are they different species Maybe o In nature these two kinds of lice do NOT breed naturally but they CAN mate and produce FERTILE offspring 0 Head lice quotraised as body licequot begin to look more like body lice in a few generations what I However the first few generations generally have high mortality rates Do they represent two biologically quotgoodquot species Yes Could they be a good ecological species Yes Human Evolution Page 1 Answer The main idea is that they are different morphotypes for the same species What About Fossils Identifying fossil species is somewhat limited to studying physical characteristics slowly changing to include genetic information We would look at how much the fossils vary between each other surface area of teeth thickness of the skull or cranial capacity Is the range of variation we see in the fossils similar to that which we see in modern species we don39t want to add to much variation to a fossil category but if we find a fossil that has more variation than we see in modern species it may be a different species Chronospecies concept a timeline of how any one lineage evolves from on species to another over time 0 Timeline of when each species lived at what point 0 Identifying the dividing line between species one and two frequently this gap happens when we have a lack of fossil records 0 Any one person may be biased here based on the traits they are focused on o This also doesn39t make it easy to find branching points which exist in most lineages Phylogenetic species concept each species must be phenotypically distinct based on fossil record 0 They must have at least one feature that others don t Must have its own evolutionary identity 0 Must have a unique pattern of descent from a single ancestor o This is also called monophyletic Species Isolation Mechanisms Premating 0 Geography or habitat they don39t overlap enough 0 Temporal having different breeding seasons 0 Behavioral mating behaviors are different 0 Mechanical they don39t have the right tools Postmating o Zygote incompatibility their sperm and eggs are unable to fertilize o Sterility all of the way to producing a hybrid which is sterile end of the line for genetic mixing U Speciation Species A and B are sympatric while A and C and B and C are allopatric Sympatric variation may happen while two species simply separate themselves while this is uncommon Two species may have an overlap zone of interbreeding they are neither completely sympatric or allopatric Polar bears and grizzly bears are mating due to their small area of overlap Human Evolution Page 2 Species Three Species Two Species One W I O Inviability no longer sustainable embryo
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