Origin and Diversification of Life:

1. Origin and Diversification of Life: Animals

2. Unit 14: Concepts • Life’s diversity explodes (I) • Animal diversity (I) • Vertebrate phylogeny (E) • Dissections (C) • Human ancestry (C)

3. Essential question 1.1: Why did life increase in diversity so suddenly during the Cambrian explosion? Ediacarans: The extent of animal life prior to the cambrian explosion

4. The ancestors of today’s organisms originated during the Cambrian period – this sudden appearance of grand diversity is referred to as the Cambrian explosion! • Organisms we see today have ancestors that developed between 535 - 505 mya. • Paleontologists uncovered many strange fossils in a mountainside in Canada called the Burgess Shale (and other rocks of similar age). • Many of these fossils are unlike anything we see today. • The survivors of this period branched out, forming today’s major groupings (phyla).

5. Burgess Shale

6. Three explanations have been made for why this sudden explosion occurred. • Environmental- The gradual increase in atmospheric oxygen eventually hit a tipping point that suddenly released animals from metabolic constraints. • Genomic - The appearance of master control genes (Hox and Pax genes) allowed minor genetic mutations (such as duplications and insertions) to produce large scale changes in anatomy. • Ecological - The onset of predator-prey relationships and the competition that resulted may have driven this explosion. • Advanced sensing had to develop prior to true hunting and escaping pressures.

7. Unit 14: Concepts • Life’s diversity explodes (I) • Animal diversity (I) • Vertebrate phylogeny (E) • Dissections (C) • Human ancestry (C)

8. Essential Question 2.1: How have specific defining characteristics been used to unite organisms within each of the major animal phyla?

9. Animals are eukaryotic multicellular heterotrophs. • Animals have many characteristics that are used to classify them. • Lack cell walls. • Require oxygen for respiration. • Most animals reproduce sexually by producing haploid cells through meiosis. • Zygotes develop through defined stages. • Morula Blastula  Gastrula • Muscle tissues allow most animals to move in many ways through many habitats. • Movement allows animals to find food or a mate. Gastrula

10. Animal Diversity • Animals are diverse in form • There are ~ 10 million living species • Only ~ 54,000 are vertebrates(possessing a backbone) • The rest are invertebrates(lacking a backbone) • There are about 36 phyla • Most occur in the sea • Three phyla dominate life on land • Arthropoda; Mollusca; Chordata

11. Major animal phyla and key evolutionary innovations • Porifera: Sponges • Muticelluarity • Cnidaria: Cnidarians • Symmetry and tissues • Platyhelminthes:Solid worms • Bilateral Symmetry • Nematodes: Roundworms • Body Cavity • Mollusca: Mollusks • Coelom • Annelida: Annelids • Segmentation • Arthropoda: Arthropods • Jointed Appendages / Exoskeleton • Echinodermata: Echinoderms • Deuterostome / endoskeleton • Chordata: Chordates • Notochord

12. Phylum Porifera are the only animals without tissues. Poriferans are asymmetrical.These sea sponges survive by filter-feeding.

13. Phylum Cnidaria are mostly marine creatures with stinging cells called cnidocytes.Cnidarians exhibit radial symmetry.Examples:Jellyfish, anemones, corals.

14. PhylumPlatyhelminthes • Flatworms • BilateralSymmetry • Planaria observed in the lab is an example of a flatworm.

15. Phylum Nematoda- • Roundworms - Body cavity • Often intestinal parasites

16. Phylum Annelida- • Segmented worms - Segmentation • Earthworm dissection in lab.

17. Phylum Mollusca have a saclike coelom(body cavity) that encloses internal organs and is often protected by a hard shell.Examples:SnailClamOctopusSquid

18. Phylum Arthropoda have an external skeleton and jointed appendages. • The most diverse phylum of animals. • Appendages allow for sensing of the environment, help obtaining food, walking, flying and digging. • 65% of all named animals (species) are arthropods. (most are insects) • High rates of reproduction contribute to their success.

19. Phylum Echinodermata exhibit radial symmetry and an endoskeleton.Echinoderms also demonstrate amazing powers of regeneration. Examples:sea stars, sea urchins, sand dollars and sea cucumbers

20. Phylum Chordata is a group of organisms with several defining characteristics.Most of chordates are vertebrates. • Pharyngeal pouches or slits • Notochord at some stage in development • Dorsal nerve cord • Post anal tail

21. Vertebrates have an endoskeleton made of bone, a vertebral column (backbone) that surrounds and protects a spinal cord and a head containing a skull and brainExamples: Class Agnatha(Jawless fish) Class Osteichthyes(bony fish) Class Chondrichthyes(cartilaginous fish) Class Amphibia(amphibians) Class Reptilia(reptiles) Class Aves (birds) Class Mammalia Common Orders of mammals Primates, Rodents, Cetacea(e.g. whales & dolphins) & Carnivora(e.g. dogs, cats, bears) More in concept 3

22. Unit 14: Concepts • Life’s diversity explodes (I) • Animal diversity (I) • Vertebrate phylogeny (E) • Dissections (C) • Human ancestry (C)

23. Essential question 3.1: What needed to occur before tetrapods could colonize the land?

24. A newly formed ozone layer allowed life to move out of the protection of the oceans. • UV light from the sun made survival on land impossible during the Cambrian period (500 mya). • However, since cyanobacteria had been producing O2 for billions of years, an ozone (O3) layer had began to form in the stratosphere. • Ozone blocks UV light from reaching Earth’s surface and protects living things.

25. During the 100 million years (440-340 mya) after their colonization, plants developed dense communities that provided food and shelter for animals. • Arthropods were the first animals to colonize land. • Colonization had to wait for the presence of a protective ozone layer and plant flora to provide a suitable habitat and food. Examples: crustaceans, insects, spiders • Insects demonstrate 2 competitive advantages that allowed them to quickly became the most diverse group of animals: • Flight • Fast rates of reproduction

26. Essential Question 3.2: How did the body plans change during the progression from fish-tetrapod-amphibian-reptile-mammal?

27. Only 4.25% of all animal species are vertebrates. • Most vertebrates are fish. • Question:With what you know of evolutionary history, why does it make sense to you that land based vertebrates are such a small fraction of the animals on Earth?

28. Vertebrates developed teeth, jaws and paired fins on the path to becoming the oceans most dominant predators. Being successful in terrestrial environments would require additional adaptations. • Jawless fish evolved about 500 mya. While lacking jaws these fish used bony extrusions (teeth) in their mouthparts to scavenge or parasitize others for food. • Jawed fish evolved about 430mya and became efficient predators. • Fish are the most successful vertebrates on Earth, making up almost half the living vertebrate species.

29. Transitional fossils like Tiktaalik roseae and several more ~375 mya(between 360 and 380mya) show many transitional forms between fish and tetrapod amphibians.It is likely that organisms of this type could not have survived on land but used adaptions like lungs and limbs to navigate shallow waters and roots to evade predation.

30. Amphibians ~360 mya, slimy skinned amphibiansrose from the oceans. • Early amphibians may have moved to a terrestrial lifestyle by the presence of insects (food) that had already made the move to land. • Two limitations of amphibian sprawl. • Amphibians must return to the water to reproduce. • Amphibians lungs are primitive compared to other terrestrial vertebrates. Most however, are able to exchange gases with the water or air via their skin as long as it remains moist.

31. Reptiles Reptiles soon established their dominance with water tight skin and eggs (350 mya). • Water tight skin / eggs prevents desiccation. • Allows some reptiles to live entire life in desert conditions. • Others, like turtles, have returned to the water. • By 240 million years, dinosaurs became the dominant land vertebrate. • During that period, land conditions were extremely dry so dinosaurs stayed the dominant land vertebrate until 65 mya. • Modern examples: Dinosaurs, snakes, turtles

32. When the age of dinosaurs ended, birds and mammals exploited the abundance of resources(65mya). • Earth’s conditions had become wetter, and reptile advantages were no longer a necessity. • Based upon structural homologies (such as skeletal structure and biochemical clues like the keratin molecules that form the structure of hair, feathers and scale) it’s clear that birds and mammals diverge from reptile ancestors. • Bird’s bodies are highly adapted for flight. • Hollow bones • Reduced body systems (example: female birds have ½ of a mammalian reproductive system) • Intelligence in mammals allowed the rise to the top of the food chain. • 5-7 mya, our ancestors diverged from the apes and began to walk upright. • By 30,000 ya, Homo sapiens walked the Earth as the sole hominid (upright) species.

33. Archaeopteryx is thought to be a transitional species between dinosaurs and birds.

34. Modern birds are successful in part due to their extreme mobility and variation.

35. Mammals Early reptiles branched into cynodonts, the precursors of mammals.

36. Cynodont reptiles evolved into modern mammals.

37. Essential question 3.3: Why does the pattern of appearance of Earth's life forms cause scientists to conclude that evolution occurred?

38. Eukaryotic evolution from Protists

39. The order and way in which these changes occurred is indicative of the evolutionary process. • The first organisms to appear were the most simple, followed by increasingly complex forms. • Large scale changes occurred with transitional forms bridging the gaps. • Major changes in Earth’s life forms coincided with major geologic and atmospheric disturbances.

40. Geologic time periods represent major geologic and biologic events.

41. Unit 14: Concepts • Life’s diversity explodes (I) • Animal diversity (I) • Vertebrate phylogeny (E) • Dissections (C) • Human ancestry (C)

42. Primates • The mammalian orderPrimates includes lemurs, tarsiers, monkeys, and apes. • There are 3main groups of living primates: • Lemurs, lorises, and pottos • Tarsiers • Anthropoids (monkeys and apes) • Humans are members of the ape group.

43. Derived Traits of Primates • Most primates have hands and feet adapted for grasping. • Other derived characters of primates: • A large brain and short jaws • Forward-looking eyes close together on the face, providing depth perception • Complex social behavior and parental care • A fully opposable thumb (in monkeys and apes).

44. A phylogenetic tree of primates Lemurs, lorises, and pottos ANCESTRAL PRIMATE Tarsiers New World monkeys Old World monkeys Gibbons Anthropoids Orangutans Gorillas Chimpanzees and bonobos Humans 40 60 50 20 10 30 0 Time (millions of years ago)

45. Nonhuman apes (a) Gibbon (b) Orangutan (e) Gorilla (d) Bonobos (c) Chimpanzees

46. Humans are mammals that have a large brain and bipedal locomotion. • The species Homo sapiensis about 200,000 years old, which is very young, considering that life has existed on Earth for at least 3.5 billion years. • Hominins(formerly called hominids) are more closely related to humans than to chimpanzees. • The study of human origins is known as paleoanthropology. • Paleoanthropologists have discovered fossils of about 20 species of extinct hominins.

47. Derived Traits of Humans • A number of characters distinguish humans from other apes: • Upright posture and bipedal locomotion • Larger brains • Language capabilities and symbolic thought • The manufacture and use of complex tools • Shortened jaw • Shorter digestive tract.

48. Timeline for some selected hominin species 0 Paranthropus robustus Paranthropus boisei 0.5 Homo sapiens Homo ergaster 1.0 Australopithecus africanus 1.5 2.0 Homo neanderthalensis Kenyanthropus platyops 2.5 Australopithecus garhi Homo erectus Australo- pithecus anamensis 3.0 Millions of years ago Homo habilis 3.5 Homo rudolfensis 4.0 Australopithecus afarensis 4.5 Ardipithecus ramidus 5.0 5.5 6.0 Orrorintugenensis 6.5 Sahelanthropus tchadensis 7.0

49. Hominins originated in Africa about 6–7 million years ago • Early hominins had a small brain but probably walked upright. • Two common misconceptions about early hominins: • Thinking of them as chimpanzees • Imagining human evolution as a ladder leading directly to Homo sapiens.

50. Australopiths • Australopiths are a paraphyletic assemblage of hominins living between 4 and 2 million years ago. • Some species walked fully erect. • “Robust” australopiths had sturdy skulls and powerful jaws. • “Gracile” australopiths were more slender and had lighter jaws.