Ecology and Paleoecology. A brief review

Transcription

1 Ecology and Paleoecology A brief review

2 Definitions Fossil assemblages Collection of fossils of organisms Lived in the same environment At the same time In the same rock record Diversity The measure of the different kinds of animals living in one area, including the number of species, genera, or family

3 Example of a fossil assemblage

4 Definitions Species: a group of similar organisms whose members freely interbreed with one another Populations: members of the same species that live together in the same area at the same time Communities: all the populations of different species that live and interact together in the same area at the same time

5 Ecosystem: A grouping of plants, animals and other organisms interacting with each other and with their environment in such a way as to perpetuate the grouping more or less indefinitely inclusive term - community together with its physical environment therefore includes biotic interaction between organisms and their interaction between organisms and their physical environment

6 Geological Time Scale and Evolutionary Change

7 Evolution The genetic change in a population of organisms over time variations favorable to survival tend to be preserved unfavorable ones are eliminated leads to adaptation evolutionary modifications that improve the survival and reproductive success of a species which might result in a new species could take millions of years

8 Change Through Natural Selection Factors of environmental resistance act as selective pressures Natural selection: the process by which evolution occurs Individuals which possess certain traits produce more viable offspring than individuals lacking those traits

9 Natural Selection Based on four premises: 1. Overproduction each species produces more offspring than will survive to maturity 2. Variation individuals in a population exhibit inherited variations in their traits

10 Figure 4-43 (p. 139) Intercontinental migrations of members of the camel family.

11 Abundance of Lifeforms (genera)

12 Taphonomy and Diagenesis: Bias in the fossil record What happened to an organism after they died and reached the fossil state is just as important as the discovery, interpretation and evolution of ancient organisms Studies of fossils can be flawed must look at fossil assemblages and environmental surroundings Ex: shallow water organisms washed into deep water; land dwelling organisms washed into water; soft-bodied organisms lost to scavengers and decay.

13 Evolution Natural selection occurs slowly. Punctuated equilibrium theory: model of evolution in which there is little change in a balanced ecosystem. A shift in the environmental conditions will alter selective pressures, thereby causing rapid changes in the species until balance is restored.

14 The honey creepers of Hawaii provide a good example of adaptive radiation. Adaptive Radiation

15 Phlyogenic trees Phylogenetic trees depicting (A) the punctuated equilibrium model and (B) the gradualistic model of evolution.

16 Range Charts Example of a range chart showing the ranges of late Cretaceous ammonite cephalopods (chambered mollusks) from the Lopez de Bertodano Formation, Seymour Island, Antarctic Peninsula. (From Macellari, E. E J. Paleontol. Mem. 18, Part 2.)

17 Use of geologic ranges of fossils to identify time-rock units

18 Figure 4-50 (p. 143) Geologic ranges, relative abundances, and evolutionary relationships of vascular land plants.

19 The Fossil Record Organization and Evolution of Life through Geologic Time

20 Fossilization Evidence of life trapped in the rock Petrifaction: turned into stone

21 Preservation without alteration Insects preserved in amber Also: Freezing of soft parts Mummification of soft parts Unaltered shells, bones, teeth, cellulose and wood Some can last thousands to millions of years without petrifaction

22 Preservation with Alteration 1. Leaching Chemical dissolution Bleached and pitted shells and/or bones 2. Recrystallization Change in crystal form Unstable aragonite to stable calcite 3. Chemical replacement Solution of original organic material and replacement with a mineral of different composition Common replacement minerals are calcite, dolomite, quartz and pyrite

23 3. Carbonization Soft tissue preserved as thin sheets of carbon Ex: plants, jellyfish, worms Sometimes the carbon is replaced by iron

24 Look familiar?

25 4. Permineralization Water containing dissolved CaCO3, silica or iron circulates through and fills pore spaces Examples: wood and bone Dinosaur tail vertebrae (left) and pliosaur tooth (right). Petrified Wood

26 Preservation Molds and casts

27 From the very big

28

29

30 To the very small..

31 Microfossils Measured in microns or m One one-thousandth of a millimeter Matrix coarser, sharper contacts, twinned crystals Microfossils fine crystals, rounded coated by organics

32 Something to think about The most stunning evidence for most of us is the presence of tiny, tubeshaped objects that resemble terrestrial microfossils. The one shown here, photographed with an electron microscope, is about 20 nanometers wide (that's only millimeters) and has segments suggestive of filamentous cyanobacteria. Cyanobacteria used to be called blue green algae. They occur as single-cellular or multicellular (filamentous) forms. Bacteria and cyanobacteria are called prokaryotes, which are organisms whose cells do not have a nucleus. Instead, they have a single strand of DNA, strung in a closed loop. (NASA photo.)

33 To evidence left behind

34 Trace Fossils Footprints, tracks and trails Burrows Borings Coprolites Chemical fossils

35 Footprints Figure 4-10 (p. 110) Dinosaur trackways arranged to indicate the passage of a biped (identical three-toed imprints) whose tracks were crossed by a quadruped having larger rear than front feet (typical of many quadruped dinosaurs).

36

37 Tracks and Trails Figure 4-11 (p. 111) Traces that reflect animal behavior: (A) crawling traces, (B) resting traces, C) dwelling traces, (D) grazing traces, and (E) feeding traces.

38 Benthic Organisms

39 Burrows and Traces Worm traces

40 Taphonomy and Diagenesis: Bias in the fossil record What happened to an organism after it died and reached the fossil state is just as important as the discovery, interpretation and evolution of ancient organisms Studies of fossils can be flawed must look at fossil assemblages and environmental surroundings Ex: shells easily broken or dissolved; bones scavenges and scattered; soft-bodied organisms lost to scavengers and decay.

41 Fossils as Environmental Indicators Provide important clues to local environment at the time when the fossiliferous rocks were formed Can also show bias shallow water organisms washed into deep water; land dwelling organisms washed into water

42 Ecology and Paleoecology A brief review