There have been 5 mass extinctions so far. A mass extinction event is defined as one that leads to a profound loss of biodiversity.

• Late Ordovician, caused by glaciation and anoxia
• Late Devonian, 70-80 percent of species went extinct due to widespread anoxia in oceans
• Late Permian or the “Great Dying” (eliminated 95 percent of species), caused by temperature rise, anoxia, and an explosion of methane-producing bacteria
• End Triassic-Jurassic, caused by euxinia (anoxic and sulfidic conditions) and acidification
• End Cretaceous (also called K-T extinction), a bolide (generic term for asteroid) moving at 45k miles per hour hit the Yucatan peninsula and threw up searing hot vapor and debris that incinerated everything in its path. The bolide also pulverized and basted into the air more than 50 times the weight of the rock, which incandesced as it fell back down through the atmosphere and generated enough heat to broil the surface of the planet. This dust contained sulfur, which kept the Earth dark for months or longer. Forests were decimated and marine ecosystems entirely collapsed. The resulting sea was completely barren and was called the Strangelove ocean.

Sulfur is particularly effective at blocking sunlight, which is why a single volcanic eruption, like Krakatoa, can depress global temperature for years.

The word amphibian comes from Greek “double life” (water and land). Gastric brooding frogs carry eggs in their stomachs and give birth through their mouths. Several North American frogs can survive the winter frozen solid like popsicles.

Chytrid fungi (called Bd) are killing frogs around the world. They are found in treetops and deep underground. Bd interferes with frogs’ ability to take up electrolytes through their skin, causing a heart attack. The chytrid fungus doesn’t need amphibians to survive, so if captive frogs were released into the wild, they would die.

In the 1950s and 60s, African clawed frogs were used as pregnancy tests. When injected with the urine of a pregnant woman, female African clawed frogs lay eggs within a few hours.

The background extinction rate for mammals is 0.25 per million species-years. Roughly 1 species disappears every 700 years.

In extinctions, once dominant organisms can arbitrarily disappear or be relegated to a secondary status. Their history of success, as in mutual funds, counts for little. In fact, traits that were advantageous for ordinary circumstances often prove disastrously disadvantageous for extraordinary circumstances. The reason we’re here has more to do with dinosaurian misfortune than any other mammalian virtue.

It took a while for scientists to even believe that species have gone extinct in the past, for example, Thomas Jefferson didn’t think this.

Ammonites = marine mollusks during Cretaceous. Went extinct because they lay eggs that float on the surface of the ocean and the sea was probably too toxic.

The effect of humans on the planet. Human activity has transformed between 1/3 and 1/2 of the planet’s land surface. Most of the world’s major rivers have been dammed or diverted. Fertilizer plants produce more nitrogen than is fixed naturally by all terrestrial ecosystems. Fisheries remove more than 1/3 of primary productivity from the ocean’s coastal waters. Humans use more than half of the world’s readily accessible freshwater runoff. The concentration of CO2 in the air has risen by 40 percent over the last 2 centuries. The concentration of methane has more than doubled.

Virtually every species that exists today is cold-adapted because they, or their close relatives, made it through the last few ice ages. For most of the Pleistocene temperatures were far lower than they are now. Glacial periods tend to last much longer than interglacial periods.

The last time temperatures were higher than they are now was during the mid-Miocene, 15 million years ago. It is possible that by the end of this century, the temperature might reach that of the Eocene, 50 million years ago. Do species still have the evolutionary traits that allowed their ancestors to survive in that warmer world but were evolutionarily costly over the last millions of years?

clinical sounding names, Reserve 112 113 120, etc.

Biological Dynamics of Forest Fragments Project in Brazil. Considered the most important ecological experiment.

• Fishbone deforestation: deforestation starts with the construction of one main road through a forest. That one road usually leads to the creation of another road, which ribs out from the original like a fishbone.