Presentation on theme: "BIOLOGY 3404F EVOLUTION OF PLANTS Fall 2008 Lecture 3 Tuesday September 23."— Presentation transcript:
BIOLOGY 3404F EVOLUTION OF PLANTS Fall 2008 Lecture 3 Tuesday September 23
Evolution We will cover the basics of evolution much more briefly than I would normally in first year G Bio. I assume that you had such an introduction to evolution in Bio 22 or 23, and that much of what we cover today (and in Chapter 11) is review. Charles Darwin and Alfred Russell Wallace are usually credited with developing the theory of evolution (both published in 1859). However, the idea of evolution was not entirely new with either
Evolution: history of an idea Anaximander (610-546? BC) believed that life arose in water, and that more complex forms arose from simpler ones. Aristotle (384-322 BC) believed that species were fixed, and do not evolve. Other Greeks held that species (including man) were originally created in their “ultimate form” and that they are all gradually degenerating over time (“devolution”).
Evolution: history of an idea, II Christian doctrine held that the Earth was created, and not ancient; Irish Archbishop James Ussher (1581-1656) put a date on the Creation at 4004 BC. How old is it? The discovery of fossils (preserved remains of prehistoric organisms) suggested a much earlier origin for Earth. French naturalist Buffon (1707-1788) raised the possibility that existing organisms had arisen from fossilized ones, but then argued against the idea.
Evolution: history of an idea, III Another French naturalist, Lamarck (1744- 1829), seriously proposed evolution, but as a mechanism proposed the inheritance of acquired characteristics. His ideas were not widely accepted, and his proposed mechanism is rejected today, but his writings served to shake existing views on special creation.
Evolution: history of an idea, IV Read about Charles Darwin’s (1809-1882) Voyage of the Beagle (1831-1836) in the text, or in his own words in Voyage of the Beagle (QH11.D2 Wheldon; online at http://www.literature.org/authors/darwin- charles/the-voyage-of-the-beagle/index.html). During his voyage, Darwin read Charles Lyell’s (1797-1875) Principles of Geology, which indicated that the Earth is old and has been formed by geological processes still at work today.
Evolution: history of an idea, V Darwin came up with his idea of “descent with modification” through the process of natural selection soon after his return in 1836, but was reluctant to publish, until spurred to do so by hearing that A.R. Wallace (1822-1903), a naturalist/collector working in Indonesia, had come up with similar ideas. On the Origin of Species by Natural Selection was first published in 1859, and shook the scientific and religious world of the 1860s (online as http://www.bookrags.com/books/otoos/index.htm).
Darwinian Evolution Darwin’s theory has two main parts: 1.Individuals vary, and species evolve as they accumulate differences from their ancestors. All living things are related through evolution to common ancestors. 2.The force driving evolution is natural selection (which can be mimicked by artificial selection), which causes individuals with features for success to replace those lacking them. This is differential reproduction: adapted individuals leave more descendants than those that are not adapted (to the particular environment where they live).
Fossils provide a lot of evidence in support of evolution. Fossils may be compressed or embedded remains, petrified (mineralized), or recorded as imprints or casts Many fossil species are clearly extinct – they do not exist today. Some are very close to existing species – fossils in western Canada of ginkgos and tulip trees that resemble modern Chinese ginkgo and tulip trees of China and eastern U.S.
Fossils, II 2.Fossils appear in historical sequence from simplest to more complex, and in a sequence of major groups: among vertebrates, from fish, then amphibians, reptiles, mammals, dinosaurs and then birds; among vascular plants, first spore-bearing, then gymnosperms, then angiosperms. 3.Fossils also provide missing links between different groups that are present today: whales with legs, showing their evolution from land mammals.
Other lines of support for evolution: 1.Biogeography 2.Comparative anatomy 3.Comparative embryology 4.Physiology 5.Molecular biology 6.Related organisms share groups of derived characters that arose in their common ancestors.
A brief geological history of Earth 4 Eras, 11 Periods, [9 Epochs] to remember P_____________ P____________ C____________ O_____________ S___________ D_____________ C____________ M_____________ P____________ P_____________ M____________ T____________ J______________ C______________ C______________ T_____________ P____________ E______________ O____________ M____________ P____________ Q_____________ P________________ H______________
Brief history of life on Earth Let’s start from the beginning: Precambrian (4500-570 MYA) big extinction 580 MYA Earth formed 4.5-4.6 BYA Life originated at least 3.5 BYA - more than likely heterotrophs feeding on simple carbohydrates [possibly 3.85 BYA, but extinguished by a meteor bombardment and re-established, survived in refuge, or “reintroduced” from outer space?] Phototrophs originated 3.4 BYA Eukaryotes originated (more than once) at least 1.5 BYA Multicellular animals by 700 MYA (and probably multicellular “protists” too) Fungi originated at least 600 MYA
Brief history of life on Earth, II Paleozoic (570-245 MYA) –Cambrian (570-510 MYA) “Explosive evolution” of phyla, including chordates –Ordovician (510-439 MYA) Major extinction event, possible invasion of land by plants –Silurian (439-408 MYA) Major extinction event, first fossil plants –Devonian (408-362 MYA) Diversification of land plants, appearance of insects, extinction of primitive land plants, first vascular plants 400 MYA –Carboniferous (362-290 MYA) “Coal Age” – age of spore- bearing vascular plants –Permian (290-245 MYA) Origin of conifers, cycads, ginkgos and replace forests of horsetails and lycopods; ends with major extinction event; 1 st vessels 260 MYA
Brief history of life on Earth, III Mesozoic (245-65 MYA) –Triassic (245-208 MYA) Forests of gymnosperms and ferns; first dinosaurs and first mammals –Jurassic (208-145 MYA) Vegetation dominated by cycads and other gymnosperms –Cretaceous (145-65 MYA) Angiosperms appear [as fossils] and diversify, become dominant; “age of reptiles”, ends with extinction of dinosaurs (and many other groups) Cenozoic (65 MYA – present) –All major groups of present-day plants have appeared; angiosperms continue to dominate and diversify, with centers of diversity based on origins and distributions at least partly based on past continental connections (continental drift = plate tectonics)
Plate Tectonics Close examination of a globe often results in the observation that most of the continents seem to fit together like a puzzle: the west African coastline seems to snuggle nicely into the east coast of South America and the Caribbean sea; and a similar fit appears across the Pacific. The fit is even more striking when the submerged continental shelves are compared rather than the coastlines.
Plate Tectonics, II In 1912 Alfred Wegener (1880-1930) noticed the same thing and proposed that the continents were once compressed into a single protocontinent which he called Pangaea (meaning "all lands"), and over time they have drifted apart into their current distribution. He believed that Pangaea was intact until the late Carboniferous period, about 300 million years ago, when it began to break up and drift apart [actually a little later – end of Permian ~250 MYA]
Plate Tectonics, III Not until the 1960's and the discoveries of features like mid-oceanic ridges, geomagnetic anomalies parallel to the mid-oceanic ridges, and the association of island arcs and oceanic trenches occurring together and near the continental margins, suggested convection might indeed be at work. These discoveries and more led Harry Hess (1962) and R. Deitz (1961) to publish similar hypotheses based on mantle convection currents, now known as "sea floor spreading".