Ch. 6 Change Over Time

Transcription

1 Ch. 6 Change Over Time

2 What Evolution is NOT! A theory that describes the origin of life on Earth. A theory that is just a theory. A theory that say that organisms TRY to adapt to their environment. A theory that stays that species turn into other species.

3 What is Evolution? A scientific theory that describes the changes in species over time. An observable and testable theory supported by a large body of evidence. A theory that explains how natural selection can result in adaptation. A theory that explains how all life has common ancestry.

4 6.1 DARWIN S THEORY

5 Charles Darwin British naturalist At 22 embarked on a five year trip to study the natural world. Observation lead him to develop the Theory of Evolution by natural selection. Determined that all species share common ancestry.

6 Voyage on the HMS Beagle Embarked in December of 1831 Took 5 years to circumnavigate the Earth Made many stops to observe plants and animals in: South America Australia Galapagos islands

7 Darwin s Observations Darwin s important observations included: Diversity of life Remains of ancient organisms Variation of characteristics of Galapagos organisms, fossil organisms, and organisms he studied in other lands. Today we know: 1.7 million species on Earth have been identified. Fossils are preserved remains of an organism. Fossils showed that some organisms no longer existed. Giant mammal fossils show extinction of giant mammals

8 Galapagos Organisms Darwin found that organisms on the islands of the Galapagos were similar to organisms on the main land. With the exception that they had specific adaptations that were unique to the Galapagos. They also had a significant about of variation in traits in the population. Examples: Finch beaks were larger and tortoise shells were taller, and iguana claws were larger.

9 The Scientific Theory of Evolution A scientific theory is a welltested concept that explains a wide range of observations. The Theory of Evolution explains the gradual change in species over time. Modes of evolution: Selective breeding- artificial selection Natural selection

10 Natural Selection The process by which individuals that are better adapted to the environment are more likely to survive and reproduce than other members of the same species. Natural Selection occurs when there is Overproduction of offspring Variation between individuals Competition for resources Selection between those that survive and those that do not Environmental Change that affects survival Natural Selection, over a long time, can lead to change in the population, or evolution. Variation in genes results in variation in traits.

11 6.2 EVIDENCE OF EVOLUTION

12 Evidence Fossils Similarities in early development Similarities in body structure- homologous structures Analogous structures Vestigial structures DNA

13 Species Relationships Scientists have combined the evidence from DNA, protein structure, fossils, early development and body structure to determine the evolutionary relationships among species. Similarities in DNA- when the DNA sequences of species are compared there is remarkable similarity. The more closely related the species are the more likely they will have similar DNA sequences.

14 Branching Trees A branching tree is a diagram that shows how scientist think that different species are related. Many types of data are used to construct branching trees. The most reliable data for constructing branching trees comes from DNA evidence.

15 New Species Formation Natural selection describes how variation in a species leads to changes in that species. New species for when a group of organisms remains isolated from its species for a long time and experience different selective pressures. This causes the group to evolve different traits than the original species. After enough time the species will be so unlike the original species it is considered a new species.

16 6.3 THE FOSSIL RECORD

17 Fossil Formation Most Fossils form when organism that die become buried in sediment, or soil and rock particles. Over millions of years the layers of sediment harden and become rock. Usually only hard parts of the organism, such as bone or shells become fossils. Petrified Fossils- remains replaced my minerals Molds and Casts- creates a hollow space that is filled with minerals Preserved Remains- ice preserves tissues of organisms

18 Determining Fossil Age Scientists can determine a fossil s age by: Relative dating: Ex. Fossils in bottom layers are older than fossil in upper layers. Radioactive dating: uses the half life or radioactive elements to determine the age of the fossil

19 The Fossil Record The fossils that have been found make up the fossil record. This record comprises the fossil information for all of known Earth and includes millions of fossils. Using the fossil record and dating methods scientists have put together a calendar or timescale of Earth s history, called the geologic timescale.

20 The Geologic Time Scale Shows the geologic history of time on Earth. Earth is 4.6 Billion Year Old Organized in Eons, Era, and Periods. Each division is marked by evolutionary, extinction or geologic events. Units of time: mya: millions of years ago bya: billions of years ago

21 4.6 bya Earth s crust solidifies with land and liquid water in the Haedon Eon (4.6 bya-3.9 bya). The Earth s atmosphere lacks oxygen and no life exists. Life first forms in the Archeozoic Eon bya. Ancient Life Life begins to produce oxygen which fills the atmosphere. (3.9 bya-2.5 bya) In the Proterozoic Eon (2.5 bya to 540 mya)soft bodied invertebrates are abundant until a mass extinction event. This event marks the end of Precambrian time around 540 million year ago. Precambrian Time

22 Phanerozoic Time 540 mya-present Known as the Eon of Visible Life Consists of the Paleozoic Era- 540 mya- 248 mya Mesozoic Era- 248 mya- 65 mya Cenozoic Era- 65 myapresent

23 Paleozoic Era 540 mya-248 mya Consists of the Cambrian Period- The Age of Trilobites Ordovician Period- land plants, primitive fish Silurian Period- jawed fish, and vascular plants Devonian Period- The Age of Fishes Carboniferous Period- Forests, insects, some reptiles and amphibians Permian Period- The Age of Amphibians

24 248 mya to 65 mya Known as The Age of Reptiles Consists of the Triassic Period- First dinosaurs, mammals- ends with a mass extinction that allows the dinosaurs to take over. Jurassic Period- Dinosaurs, flowering plants,- ends with a minor extinctions. Cretaceous Period- Dinosaurs rule, and feathered dinosaurs appear- high geologic activityended with mass extinction event- end of dinosaurs and about 50% of life. Mesozoic Era

25 Cenozoic Era 65 mya- present Known as The Age of Mammals Consists of the Tertiary Period- diversity in mammal population- first primates, first hominids, modern birds, Quaternary Period- The Age of Man- large mammals, primates, hominids, homo sapiens, last mass extinction event 10,000 year ago killed large mammals- probably caused by the end of the last ice age.

26 Evolution Events First evidence of life (3,850mya]) Oldest fossils (3,500 mya) First evidence of soft-bodied animals (900 mya) The Cambrian Explosion (530 mya) First land plants and fish (480 mya) First reptiles (350 mya) First mammals and dinosaurs (220 mya) First birds (150 mya) First hominids (5.2 mya) Modern humans (0.1 mya)

27 There have been 5 major extinction events in geologic time. Most of the major extinction event are attributed to volcanic activity, asteroid impact, ice age or a rapidly warming or cooling climate. Some single-celled animals and softbodied animals (End of the Precambrian 543 mya) Reef-builders and other shallowwater organisms ( End Cambrian ( Late Odrovician 520 mya) P-T extinction- Ninety percent of all species (End Permian 250 mya) K-T extinction- Dinosaurs and 60 to 80 percent of all species (End Cretaceous 65 mya) Foraminifera, gastropods, and sea urchins ( Tertiary Period 33 mya) Many woodland, plant-eating herbivores (Miocene 9 mya) Nearly all mammals and birds over 45 lbs. (Quaternary Period 0.1 mya) Extinction Events

28 Geologic Events -Formation of the great oceans (4,200 mya) -Continents begin shifting (3,100 mya) -Rodinia supercontinent breaks up (700 mya) -Gondwana forms (500 mya) -Great mountain ranges form (425 mya) -Formation of Pangaea supercontinent (280 mya) -Pangaea supercontinent breaks up (200 mya) -Mt. Stuart and the Stuart Range is formed (96 mya) -Ancestral Cascade Mountains form (37 mya) -Inland seas dry up (20 mya) -Columbia River Basalts (17 mya) -Global ice ages begin (2 Mya)

29 The Evolution of Life m/watch?v=h2_6cqa2cp4 3.8 billion years of evolution has filled the earth with a diversity of organisms. The first to appear were single celled. Followed by multicellular life in water, then on land.

30 The Evolution of Hominids Hominids- upright walking human like primates All other species of hominids are extinct except for humans, Homo sapiens. Hominids share a common ancestor with the great apes. Other hominid species Homo neanderthalensis Homo erectus Homo habilis Australopithecus africans Australopithecus afarensis (lucy)

31 Unanswered Questions Mass Extinctions: Exact causes of mass extinctions are unknown but most are attributed to climate change, asteroid collisions, or volcanic eruptions. Gradualism Theory: Evolution occurs slowly but steadily, small changes add up major changes over very long periods of time. Punctuated Equilibria: The theory that accounts for gaps in fossil record, where species evolve quickly during short periods. The periods of rapid change are followed by long periods of little or no change.