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Transcript
Evolution Review What this unit focused on! Here Today, Gone Tomorrow? Key concepts Making decisions about complex issues often involves trade-offs Many life forms have gone extinct in the past. Extinction can be related to environmental changes. Extinct species often have living relatives, i.e. closely related species that live on after them. Here Today, Gone Tomorrow? Extinct mammoths are more closely related to Asian Elephants than African Elephants. Could we? Should we? Re-create the mammoth? Fossils Fossils: Help us determine features & behaviors major source of evidence used to determine relationships among species Used to develop theory of evolution Come from bones, nails, teeth, etc. Earth is about 4.5 billion years old and life forms have existed on it for over 3.5 billion years. Geological Time Line Know the geological timeline – know which major developments happened where Bacteria Protozoa Age of Fishes Age of Reptiles Age of Dinosaurs Age of Mammals The Great Extinction The Second Great Extinction Pangaea Flowering Plants Bees Horses Humans Geologic Time Scale Earth = 4.6 bya Oldest evidence of life = 3.5 bya The divisions of the geologic time scale are determined by the first or last appearance of certain fossils in the fossil record. Several mass extinctions have occurred = CATASTROPHISM Geologic Time Scale The time scale does not divide the history of Earth into blocks of equal duration. The boundaries between sections are defined by the first or last appearance of certain fossils in the fossil record. Reading the Rocks Law of Superposition Older rocks are at the BOTTOM Younger rocks are at the TOP A Meeting of the Minds Many life forms have gone extinct in the past. Extinction can be related to environmental changes. Variations occur naturally within populations, and provides the raw material for natural selection. Only inheritable traits are transmitted by reproduction and thus can change over generations due to natural selection. Competition for survival and reproduction determines which genetic traits are more likely to be transmitted to future generations. A Meeting of the Minds Darwin Lamarck Jean-Baptiste Lamarck’s theory Inheritance of acquired characteristics Frequent and vigorous use of a body part led to a slight increase in its size. These changes were heritable and could lead to an entire population to transform gradually over time. Charles Darwin’s Theory Adaptations occur over many generations by a population. MAIN CONTRIBUTION: variation exists within any population and leads to natural selection Charles Darwin and Alfred Wallace Known as “Natural Selection” 1. Variation within a species occurs naturally 2. Organisms must compete for limited resources to survive. 3. The individuals that are better suited for the current environmental conditions survive and reproduce more often than the others do 4. As a result, the genes and traits that are most common in a population can change through time. Which stars are best suited for the environment? Which stars are best suited for the environment? Battling Beaks Competition for survival and reproduction determines which genetic traits are more likely to be transmitted to future generations. Under different environmental conditions, natural selection acts upon the same species differently. Genes Mutate. Individuals are selected. Populations evolve. Battling Beaks Random mutations during DNA replication continually introduce new variation into all populations. Origins of Species Mutations can be advantageous, disadvantageous, or neutral Under different environmental conditions, natural selection acts upon the same species differently, favoring different variants; this can lead to speciation. Origins of Species Darwin found: Each species has a particular role within its ecosystem. Variation occur & get passed onto new generations. Mutations cause variation. Darwin and the Galapagos Islands Family Histories Single-celled organisms Multi-celled invertebrates Fish Amphibians Reptiles Birds Mammals Family Histories Family Histories Fish appeared first in the early Paleozoic Era Reptiles appeared next in the late Paleozoic Era Mammals appeared in the Mesozoic Era but many more mammals appeared during the Cenozoic Era. A Whale of a Tale Use skeletons & fossils to trace changes in anatomy over time Natural selection explains changes (adaptations) Modern whales evolved from small land dwelling mammals Whales! A Whale of a Tale Land creatures evolved into sea creatures The stepwise shift in habitat from land to shallow water to open ocean involved many adaptations, which occurred in large part over the 20 million years between about 55 and 35 million years ago. Shift of nostrils Streamlining the body shape Reduction and elimination of hind legs Transforming the forelimbs into flippers Strengthening of the tail Addition of tail flukes Modification of ears and eyes Loss of most hair Acquisition of a layer of insulating blubber