Evolution Notes Adapted from: www.biologycorner.com What is Scientific Theory Inscience, theories are hypotheses or models that have been tested and confirmed many times. Example of a theory: Gravity In science, the term "Theory" does not express doubt. They explain a wide variety of data and observations They can be used to make predictions They are not absolute, can be changed as new evidence is found The theory of evolution is considered a Unifying Theory of Biology, because it answers many questions and offers explanations for observations. History of Evolution Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION – which explained how organisms changed over time (ADAPTED) Lamarck's Theory of Acquired Characteristics – Some thought that you would gain or lose features if you overused or didn't use them, – PROVEN TO BE WRONG! Key Points 1. Variation exists among individuals in a population. 2. Some variations are favorable. 3. Not all young in a population can survive 4. Individuals that survive and reproduce are those with favorable variations. – This process came to be known as Natural Selection – The favorable variations are called Adaptations Evidence of Evolution Fossils Evidence from Living Organisms – Homologous Structures – Analogous Structures – Biochemistry and DNA – Vestigial Structures Observed Changes Bacteria become resistant to antibiotics Wolves were bred over many generations to become dogs (artificial selection) – then bred further to create a variety of breeds Taxonomy The Science of Classifying Organisms Why do we need to classify? Imagine a store….. – how do you know where to find the milk or the cereal? Are they in the same aisle? – How is the store “organized”? Are all stores similar? Imagineyour computer or mp3 player….. – are all of your songs and files in a single folder or do you have them grouped in some way? When you have a lot of information, it is best to organize and group items so that you can find them easier or easily see their relationship to other items ...this is why we CLASSIFY Even websites must organize their products Scientists also need a way to “NAME” organisms The “common names” used by people can sometimes be misleading or confusing In order to communicate effectively, biologists need a CONSISTENT naming protocol. *Check out these slides of confusing names….. Sea Lion Ant-lion Lion Which one of these is NOT actually a bear? What kind of organism is it? (invertebrate, mammal, insect, fish, reptile…) 1. Sea Monkey 2. Firefly 3. Ringworm 4. Jellyfish 5. Spider monkey 6. Crayfish 7. Sea Horse Consider this… Are all “Grey Wolves” gray? Are all “Black Bears” black? Which is more venomous…a water moccasin or a cottonmouth? – Grey wolves can be white, black and any shade of gray. – Black bears can also be brown or gray – A cottonmouth and a water moccasin are the same animal – the names vary by region. Naming and Organizing are part of the same process The system was developed by Carolus Linnaeus who used Greek and Latin names for organisms He also created a system where we place all organisms into a few “large” groups - KINGDOMS - and then those groups are further divided into smaller groups Grouping Kingdom Phylum Class Order Family Genus Species Each group gets smaller and more specific – just think of the way you file things on your computer into folders and subfolders To help you remember the list… KING PHILIP CAME OVER FOR GREAT SOUP Kingdom, Phylum, Class, Order, Family, Genus, Species Humans Kingdom Animalia Phylum Chordata Class Mammalia Order Primate Family Homindae Genus Homo Species sapiens The scientific name is always the genus + species Humans = Homo sapiens Lion Tiger Pintail Duck Kingdom Animalia Animalia Animalia Phylum Chordata Chordata Chordata Class Mammalia Mammalia Aves Order Carnivora Carnivora Anseriformes Family Felidae Felidae Anatidae Genus Panthera Panthera Anas Species leo tigris acuta More on Naming… The system of naming is called BINOMIAL NOMENCLATURE - which means it is a 2- name system. Scientific names must either be underlined or italicized The genus is always capitalized, the species is lowercase Can be abbreviated. Ex. P. leo and P. tigris What is a species? Defined as organisms that can interbreed with one another, and produce fertile offspring. When two organisms of different species interbreed, the offspring is called a HYBRID Check for Understanding 1. Fill in the blanks: Kingdom, _____________, Class, Order, ________________, Genus, _______________ 2. Which two groups are used for an organism's scientific name? 3. Which of the following pairs is MOST closely related? Acer rubrum & Acer saccharum Acer rubrum & Chenopodium rubrum 4. The system we use for naming is called ____________ nomenclature. 5. The science of classification is called ____________ The Kingdoms There are currently 5 Kingdoms – all organisms can be placed into one of those 5. Classification into a Kingdom is based on certain criteria – Number of cells (unicellular or multicellular) – How it obtains energy (feeding) – Type of cell Eukaryote (all have nucleus) Prokaryote (do not have a nucleus) Protist Kingdom Unicellular; microscopic Nucleus present – Eukaryotic Autotrophic or heterotrophic Classified by how they move Plant like: Phytoplankton – Provide 90% of worlds oxygen Animal like: Zooplankton – Their remains are used in cleansers such as toothpaste and comet Bacteria Kingdom Unicellular, microscopic Motile (Move) No nucleus – Prokaryotic No chlorophyll – Decomposers (Saprophytic) – Parasitic E. Coli: food poisoning (deadly) – Normally found in intestines – Beneficial Lactobacillus: yogurt and cheese Fungus Kingdom Eukaryotic Non-motile (don’t move) No root, stem and leaf No chlorophyll – Decomposers – Saprophytic or parasitic Reproduce by forming spores Most are Multicellular: mushrooms, bread mold etc.. Unicellular: yeasts Plant Kingdom Eukaryotic Non-motile (don’t move) Most plants contains pigments (chlorophyll) for photosynthesis – Autotrophic Can be divided into two groups: – Non-flowering plants – Flowering plants Animal Kingdom Which of these is an “animal”? Answer: They are all animals! Characteristics of Animals: 1. Heterotrophic 2. Eukaryotic 3. Multicellular 4. Lack cell walls. Dividedinto two groups according to the presence or absence of backbone: – Invertebrates : No Backbone Sponges, Cnidarians, Flatworms, Round worms, Mollusks, Segmented Worms, Arthropods, Echinoderms, – 95% are Invertebrates – Vertebrates : Backbone Fish, Amphibians, Reptiles, Birds, Mammals – 5% = Vertebrates Functions of Animals 1. Feeding a. Herbivore = eats plants b. Carnivore = eats animals c. Omnivore = eats plants and animals d. Decomposer = feed on decaying organic material e. Filter Feeders = aquatic animals that strain food from water f. Parasite = lives in or on another organism (symbiotic relationship) 2. Respiration •Take in O2 and give off CO2 •Lungs, gills, through skin, & simple diffusion 3. Circulation •Very small animals rely on diffusion •Larger animals have a circulatory system 4. Excretion Primary waste product is ammonia 5. Response Receptor cells = sound, light, external stimuli Nerve cells => nervous system 6. Movement * Most animals move 7. Reproduction Most reproduce sexually = genetic diversity Many invertebrates can also reproduce asexually to increase their numbers rapidly Body Symmetry The body plan of an animal, how its parts are arranged • Asymmetry - no pattern • (corals, sponges) • Radial Symmetry - shaped like a wheel • (starfish, hydra, jellyfish) • Bilateral Symmetry - has a right and left side • (humans, insects, cats, etc) Identify the Symmetry Body Sides anterior - toward the head posterior - toward the tail dorsal - back side ventral - belly side Cephalization An anterior concentration of sense organs (to have a head) *The more complex the animals becomes the more pronounced their cephalization. Octopus – member of the class Cephalopoda (head-foot) Segmentation “Advanced" animals have body segments, and specialization of tissue (even humans are segmented, look at the ribs and spine) Body Types… • Depends on the presence or absence of a coelom (body cavity). • Body types are relative to how animals are classified… Acoelomate: lacks a body cavity. Pseudocoelomate: posses a fluid filled cavity between the endoderm and mesoderm. (Roundworms and Hydra) •Differs from a true coelomate because organs are not entirely lined with mesoderm tissue. Coelomate: a true body cavity forming within the mesoderm. (Segmented worms, Muscles, Arthropods, and Chordates.) • Coelomates fall into either the protostomes or deuterostomes category depending on how their embryos develop. Embryo Development • Animals begin life as a zygote •Fertilized egg •The zygote divides to form the blastula • a hollow ball of cells • The Blastula then goes through process of gastrulation • creating the blastopore • first opening in the blastula •re-arrangement of the cells into three germ layers • becoming specific structures in the animal. Germ Layers Endoderm: Innermost layer: becomes the lining inside the body cavity – the digestive and respiratory tract Mesoderm: Middle layer: becomes the organs inside the body – muscle, circulatory, reproductive, and excretory systems Ectoderm: Outermost layer: becomes the body covering. – outer layer of skin, sense organs, and nerves Protostome and Deuterostome Protostomes: "first mouth" blastopore develops into a mouth. Deuterostomes: "second mouth" blastopore develops into an anus mouth forms second hence the naming of "second mouth". Vertebrates are deuterostomes. Body Plans Mostanimals have a "tube-within-a-tube“ body plan. – This calls for two openings: one for food to enter the body (mouth) one for wastes to leave the body (anus) This plan allows for specialization of parts, such as a stomach, intestine, etc. Animals with the "tube-within-a-tube" plan are 10% more efficient at digesting and absorbing their food than animals with the sac-like body plan. Some animals have a “sac-like” body plan. – has only one opening for both food intake and waste removal. – No tissue specialization or development of organs. Animal Kingdom Phyla Phylum Porifera – Sponges Phylum Cnidaria – Sea anemones, jellyfish, hydra -Jelly like animals that have a bell or umbrella shape Phylum Platyhelminthes -Flatworms - Soft, thin, and flat bodies Free-living Planarian Parasitic Tapeworm Phylum Nematoda – Roundworms Phylum Annelida – Segmented worms Phylum Mollusca Clams, squid, snails -Soft bodied, usually with a shell Phylum Arthropoda – Crustaceans, insects, spiders This is the largest phylum in the animal kingdom and contains the most number of species They have 3 body parts, jointed legs, and a tough exoskeleton. Phylum Echinodermata Starfish -Marine animals have plates with spines Phylum Chordata Includes all vertebrates -Notocord (backbone) Taxonomy Clades and Keys Evolutionary Classification Phylogeny = the study of evolutionary relationships Biologists now group organisms into categories that represent evolutionary descent, not just physical similarities. How would you classify a hyena? Would you group it with cats or dogs? Derived Characters Characteristics that appear more recently in a group but are not seen in older organisms Derived characteristics are used to construct a CLADOGRAM – a diagram that shows evolutionary relationships Cladograms A diagram that shows evolutionary relationships HOW TO BUILD A CLADOGRAM Watch this animation on how to build a cladogram http://ccl.northwestern.edu/simevolution/ obonu/cladograms/Open-This-File.swf Identifying Unknown Organisms When biologists do field studies, they often encounter new specimens that they would need to identify Field Guides often contain pictures for referencing organisms Dichotomous Keys A step-by-step guide to help identify an organism. – Which follows a series of choices that lead you to the organism’s name. Check for Understanding 1. A diagram that shows an evolutionary relationship is a _______________. 2. A characteristic that appears only in recent members is called a __________ character. 3. The study of evolutionary relationships is called _________. 4. A system to find the name of an unknown organism is a _________ key.
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