What type of life do you think can be found in Antarctica? The coldest continent on Earth The coldest temperature ever recorded was -89.2° C, or -128.6° F, not including wind chill! What type of life do you think can be found in Antarctica?

Fossils found in Antarctica Fossilized Fern Fossilized Dinosaur Jaw Bone How could Antarctica’s climate support plant life & large animals?

…but how could closely related species live on different continents? Scientists have found fossils in Africa, India, & Antarctica that look very similar to each other. It seems like the fossils belong to species that are closely related… …but how could closely related species live on different continents?

The fossils belong to Lystrosaurus, a group of extinct vertebrates that lived about 250 million years ago. Lystrosaurus murrayi

Fossils can be found all over the world. Studying the distribution of fossils (& living species) can help us understand how species are related.

Fossils that occupy continuous areas can indicate common ancestry among species that live on different continents!

Biogeography

Biogeography The geographic distribution of living & extinct organisms

Many species had differences depending on which island they came from. The Galapagos Islands A group of islands off the coast of South America – Darwin sailed here in 1835 & made many observations. The islands are home to many unique species found only on those islands, but they’re similar to those on the mainland. Many species had differences depending on which island they came from.

The Unique Species of the Galapagos Islands The native people could tell which island a tortoise came from by looking at the shape of its shell. Darwin saw a different species of finch on each island. Each species of finch had a different type of beak, depending on the food available on its island.

The Unique Species of the Galapagos Islands Are the different species closely related? Are they related to similar species on the mainland (Ecuador)?

How & why did species on the Galapagos evolve? i. Each island habitat has different selective pressures acting on the organisms.

Remember – a selective pressure is any factor that makes it hard for some organisms to survive, but rewards any advantage that some organisms may have been born with. Food availability varies from island to island. On an island where food is not easily found, only the best adapted will survive. What is the selective pressure in this example?

How & why did species on the Galapagos evolve? ii. Natural selection acts on the populations separately, which over time, causes the populations to diverge morphologically & physiologically. Food on Hood Island is sparse, so turtles are smaller. Their saddle-backed shells allow them to lift their necks higher to reach vegetation. Food on Isabela Island is common & can support larger turtles.

The different species of finches on the islands all evolved from a common ancestor in Ecuador. Since each island is different, the finches on each island evolved in response to different selective pressures. Over time, the finches began to differ according to the food supply available on the island.

How are the beaver & capybara similar? The beaver & the capybara live in similar environments, so they respond to similar selective pressures. Because they respond to similar selective pressures, they’ve evolved similar features & adaptations. Can we say that the beaver & capybara are closely related?

NO! They’re not closely related. Organisms that are unrelated in the same types of habitats elsewhere in the world had the same selective pressures acting on them, & therefore, developed similar characteristics. Analogous Structures The beaver & the capybara are not closely related. However, they live in similar environments, so they have similar features.

How long has life been evolving on Earth? Scientists have created the Geologic Time Scale which identifies major events that occurred in the past. Fossil record shows us that Earth is about 4.6 billion years old!

The Geologic Time Scale Glaciations; mammals increased; humans Mammals diversified; grasses Aquatic reptiles diversified; flowering plants; mass extinction Dinosaurs diversified; birds Dinosaurs; small mammals; cone-bearing plants Reptiles diversified; seed plants; mass extinction Reptiles; winged insects diversified; coal swamps Fishes diversified; land vertebrates (primitive amphibians) Land plants; land animals (arthropods) Aquatic arthropods; mollusks; vertebrates (jawless fishes) Marine invertebrates diversified; most animal phyla evolved Anaerobic, then photosynthetic prokaryotes; eukaryotes, then multicellular life Cenozoic Mesozoic Paleozoic Precambrian Time Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian 1.8–present 65–1.8 145–65 208–145 245–208 290–245 363–290 410–363 440–410 505–440 544–505 650–544 Key Events Era Period (millions of years ago)

According to the geologic time scale, life has been around for millions of years. The evolution of life on Earth is well documented. The origin of life on Earth is still a puzzle…

Prokaryotic cells evolved first. The Origin of Life What types of cells do you think came first – prokaryotic or eukaryotic? Prokaryotic cells evolved first. They’re smaller, more simple, & don’t have complex organelles.

Endosymbiosis The relationship in which 1 organism lives within the body of another. Eukaryotic cells may have evolved through endosymbiosis.

Mitochondria & chloroplasts in eukaryotic cells provide evidence of endosymbiosis.

Before you leave… On a sheet of paper (share!), describe why this cartoon is inaccurate.