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Evolution, Natural Selection and the Diversity of Animals How do new species begin? • DNA is instructions for all life • DNA - RNA Protein Trait • Mutations MAY cause changes in the production of proteins • New traits can be passed to offspring – May be helpful, bad or cause no change at all Mutations • Changes in the DNA sequence of nucleotides: A’s, G, C’s and T’s – – – – – – – – – Sickle cell anemia – Harmful? Helpful? Albinism Cystic fibrosis Most diseases and deformities Blond or brunette 2 legs or 4 legs? Fins or flippers? Color of skin All differences! Mutations: the good, the bad, and the indifferent • Point mutations – one letter change; substitution • Frame-shift mutations – insertion or deletion of one or more nucleotides that “shifts” information; • each 3 code for 1 amino acid that makes up a protein • EX: cat ate the ratcatatetherat • caatatetherat Caa tat eth era t • Ctatetherat Cta tet her at Mutations can change a population • If new traits is advantageous, • those w/ trrait will have more successful offspring than those without it • Over long periods of time… • populations -- new species • Fish w/ lungs move onto land reptile humans! • Species = groups that are so similar they can breed with each one another and produce VIABLE (capable of reproducing) offspring. This is Natural Selection. New species can develop if… • Members of a populations are separated from each other (GEOGRAPHIC ISOLATION) • Members of two populations can no long breed successfully with one another (REPRODUCTIVE ISOLATION) • Having an abnormal number of chromosomes (POLYPLOIDY) Divergent Evolution • One ancestral species leads to 2 new species Marine Iguana Land Iguana Ancestral Green Iguana Adaptive Radiation • One ancestral species leads to 3 or more new species Types of Evolution Two ideas of how new species develop • Gradualism: lots of small changes in DNA over long periods of time • Punctuated Equilibrium: fewer, larger changes over long periods of time. Gradualism 10 million years Punctuated Equilibrium 10 million years Notice the results of both are the same: CHANGE Evidence for evolution • Antibiotic resistant bacteria • Fossils • Anatomy • Embryology • Biochemistry All of these methods are used together to show relationships between species Fossil Record Used to observe early life: • Incomplete – only hard parts fossilize in specific types of soil • Like a puzzle – overall pattern Anatomy • Similarity in structures suggests relationships between animal species • Homolgous and Analogous structures – see diagram • Vestigial structures – whale pelvis Homologous and Analogous Structures • Homologous structures (homo=same) – alike because they are closely related Example: bird wings, bat wings, your arm and hand • Analogous structures (not closely related, but same function) - -bird wings and insect wings Embryology • sperm + egg fertilization zygote (1 cell) • blastula – about 64 cells • gastrulation – when blastula begins to fold in – Forms opening into gastrula – gastrula – 2 cells layers = 2 tissue layers • archenteron – opening into the gastrula Protostome vs Deuterostome If the archenteron (opening) forms into: • a mouth first = PROTOSTOME • an anus first = DEUTEROSTOME • All invertebrates (no backbone) are protostomes except echinoderms • Vertebrates (w/backbone) and echinoderms = Deuterostomes • Humans? Living things are grouped according to similarities • Embryology The more similar the embryonic development pattern the more closely related Embryology Vertebrate embryos share developmental characteristics: – – – – Post anal tails Pharyngeal slits or pouches Notochords Nerve cords DNA determines these characteristics! Biochemistry • All organisms have DNA, ATP, and other enzymes/proteins in common • DNA is made of 4 molecules: A,T,C, and G • Similar DNA sequences = similar ancestry A cladogram is like a family tree showing how things have changed. Shows relationships based on specific characteristics Point where common ancestors diverged Everything to the right of this point have Vertebrae Living things are grouped according to similarities • • • • • • • Kingdom Few similarities Largest # of organisms Phylum Class Order Family Genus Species Most similarities Smallest # of organisms Binomial Nomenclature: scientific names are Genus and Species Ex: Iguana iguana, Homo sapien Living things are grouped according to similarities HOMOLOGOUS structures, humans, birds, porpoises and elephants are considered more closely related to each other than any are to insects. Dichotomous keys • Species can be identified using a dichotomous key • Series of “either / or” questions leading to the identification. Dichotomous keys Example: 1. Does the flower have white or yellow petals? -if yellow, it is a sunflower -if white, go to question 2 2. Does the flower have a yellow or red center? -if yellow, it is a daisy -if red, go to question 3