History of Life on Earth

Transcription

1 Macroevolution Broad pattern of evolution at and above the species level (in contrast to microevolution) History of Life on Earth Chapter 25 Early earth Miller and Urey Experiments ~4.5 billion years old Effect of volcanic eruptions Deep Sea Hydrothermal Vents 1

2 Formation and function of protocells Fossils show earth s history Nature of fossils Biased in favor of long-lived species with hard shells in certain environments favorable to fossilization Dating fossils An example of relative dating 2

3 Absolute dating uses radioactive decay The geologic record Major boundaries between geological divisions match extinction events in the fossil record Life on earth in perspective The first single-celled organisms Stromatolites are rock-like layers of prokaryotic films Photosynthesis and oxygen Cyanobacteria were early photosynthesizers Increased oxygen most likely negatively impacted prokaryotes Cellular respiration becomes important The first eukaryotes Arose through endosymbiosis 3

4 Evidence for endosymbiosis Inner membranes are similar to plasma membranes of prokaryotes Division is similar in these organelles and some prokaryotes These organelles transcribe and translate their own DNA Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes Multicellularity The Cambrian explosion Colonization of land Adaptations to avoid water loss were important Tectonic plates move land surfaces in a process called continental drift Land movement affected the history of life Movement promoted allopatric speciation Movement changed environmental conditions Movement explains biogeography, the geographic distribution of organisms 4

5 Diversity has increased and five mass extinctions have occurred K-T extinction Sixth mass extinction Currently underway Scientists estimate that the current rate of extinction is 100 to 1,000 times the typical background rate Only extinction due to activities of an organism Habitat destruction Overharvesting Pollution Extinction rate increases with global temperature Adaptive radiation increases diversity rapidly Key adaptations and/or opportunity can lead to adaptive radiation 5

6 Heterochrony Macroevolution can occur through changes during development A change in the rate of development or change in the timing of development For example, differential development times in skulls during development create different phenotypes Homeotic genes Changes in gene change phenotype Determine pattern such as where wings and legs will develop on a bird or how a flower s parts are arranged Changes in these genes change patterns in organisms Changes in gene expression change phenotype 6

7 Radiometric dating. a) can be used to directly date fossils in sedimentary rock b) relies on the fact that the daughter isotope decays to the parent isotope at a constant rate c) allows us to indirectly date fossils up to billions of years old based on minerals in surrounding volcanic strata d) works only on rocks younger than 75,000 years e) allows us to determine an absolute, errorless date You discover three fossil organisms and want to determine their dates. You measure the percentage of carbon-14 (half-life 5,730 years) remaining in the fossils. Which of the following correctly places them in order from oldest to a) A, B, C youngest? b) B, C, A c) C, A, B Fossil % 14 C d) A, C, B A 38.7 B 77.0 C 52.1 If the mitochondria and chloroplasts in eukaryotic cells resulted from endosymbiosis, what feature(s) might we expect these organelles to contain? a) a plasma membrane, DNA, and ribosomes b) a plasma membrane, nucleus, and ribosomes c) nucleus, DNA, and ribosomes d) a plasma membrane, nucleus, and cilia e) nucleus, ribosomes, and cilia 7