BIOL1030 Lecture Notes - Lecture 12: Plate Tectonics, Ordovician, Convergent Evolution
Lecture 12 notes- Mass Extinctions
Convergent evolution occurs when two or more unrelated species because more similar to another
because they adapt to similar conditions of natural selection
Why is convergence important?
- All organisms take advantage of a particular part of the environment
- If a specifically adapted species goes extinct, another will be under natural selection to
replace it
- Example: Herbivores through the ages take advantage of plants to feed themselves. If they
go extinct, other groups of animals will evolve convergent adaptions to plant eating
- There have been herbivorous crocodiles
ORDOVICIAN- SILURIAN MASS EXTINCTION
435 mya
Causes: two distinct die-offs, coincidental of climate change (cooling), earth tectonic plate
movement was final collapse
Extent: 85% of marine species (there were no terrestrial animals yet)
Life before the Ordovician- Silurian extinction
Top predators- Big Cephalopods (squid relatives with external shell)
Herbivores- Filter feeders such as bryozoans and sponges; Trilobites
Missing- most vertebrates, land animals
Life after the Ordovician- Silurian extinction
Top predators- Sea scorpions (arthropods), agnathans (jawless) fish, cephalopods
Herbivores- Plankton feeders, corals, trilobites
Convergent replacement- Cephalopods vs. sea scorpions and Bryozoan/sponge vs coral reefs
DEVONIAN-CARBONIFEROUS MASS EXTINCTION
355 mya
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Convergent evolution occurs when two or more unrelated species because more similar to another because they adapt to similar conditions of natural selection. All organisms take advantage of a particular part of the environment. If a specifically adapted species goes extinct, another will be under natural selection to replace it. Example: herbivores through the ages take advantage of plants to feed themselves. If they go extinct, other groups of animals will evolve convergent adaptions to plant eating. Causes: two distinct die-offs, coincidental of climate change (cooling), earth tectonic plate movement was final collapse. Extent: 85% of marine species (there were no terrestrial animals yet) Top predators- big cephalopods (squid relatives with external shell) Herbivores- filter feeders such as bryozoans and sponges; trilobites. Top predators- sea scorpions (arthropods), agnathans (jawless) fish, cephalopods. Convergent replacement- cephalopods vs. sea scorpions and bryozoan/sponge vs coral reefs. Causes: environmental change because forests developed on land, climate change, invasive species taking over and preventing speciation.
