1. Ch. 26 : Animal Evolution and Diversity

2. 26.1 Invertebrate Evolution and Diverisity

3. Origins of the Invertebrates
3 billion years ago, prokaryotes and eukaryotes were single-celled.
Animals evolved from ancestors they shared with organisms called choanoflagellates

4. Traces of Early Animals
The first animals were tiny and soft-bodied, so few fossilized bodies exist.
As animals became larger and more complex, specialized cells joined together to form tissues, organs, and organ systems that work together to carry out complex functions.
Trace fossils are tracks and burrows made by animals whose body parts weren’t fossilized

5. The Ediacaran Fauna
Fossils from The Cambrian Period date back roughly 565 to about 544 million years ago.
They show little evidence of cell, tissue, or organ specialization, and no organization into a front and back end
Many of the organisms were flat and lived on the bottom of shallow seas.

6. The Cambrian Explosion
Cambrian fossils show that over a period of million years, animals evolved complex body plans, including specialized cells, tissues, and organs
Many had body symmetry; segmentation; a front and back end; and appendages, structure such as legs or antennae protruding from the body.
By the end of the Cambrian Period, all the basic body plans of modern phyla had been established.

7. Modern invertebrate Diversity
All invertebrates except sponges exhibit some type of body symmetry—either radial symmetry or bilateral symmetry.
Invertebrates with cephalization can respond to the environment more quickly and in more sophisticated ways than can simpler invertebrates.
Worms, arthropods, and mollusks are protostomes, and echinoderms are deuterostomes.

8. Nonchordate Invertebrates
The cladogram of nonchordate invertebrates presents current hypotheses about evolutionary relationships among major groups of modern invertebrates.
These features include body symmetry, cephalization, segmentation, and formation of a coelom.

9. 26.2 Chordate Evolution and Diversity

10. Origins of the Chordates
Chordates are the animals we know best because they are generally large, often conspicuous, and strike us as beautiful, impressive, cute, or frightening.
Some we keep as pets, others many of us eat as sources of protein.

11. The Earliest Chordates
Embryological studies suggest that the most ancient chordates were related to the ancestors of echinoderms.
In 1999, fossils beds from later in the Cambrian Period yielded specimens of Myllokunmingia, the earliest known vertebrate.
Cartilage is a strong connective tissue that is softer and more flexible than bone.

12. Modern Chordate Diversity
Modern chordates are very diverse, consisting of six groups: the nonvertabrate chordates and the 5 groups of vertebrates- fishes, amphibians, reptiles, birds, and mammals.
About 96% of all modern chordate species are vertebrates.
Among vertebrates, fishes are the largest group by far,

13. Cladogram of Chordates
The cladogram of chordates presents current hypotheses about relationships among chordate groups.
It also shows at which points important vertebrate features, such as jaws and limbs, evolved.

14. Nonvertebrate Chordates
The nonvertebrate chordates are tunicates and lancelets.
Adult tunicates look more like sponges than us.
They have neither a notochord nor a tail, but their larval firms have all the key chordate characteristics.

15. Jawless Fishes
Lampreys and hagfishes both lack vertebrae and have notochords as adults.
Lampreys are filter feeders as larvae parasites as adults.
Hagfishes have pinkish gray, wormlike bodies, secrete incredible amounts of slime, and tie themselves into knots!

16. Sharks and their Relatives
Jaws hold teeth and muscles, which make it possible to bite and chew plants and other animals.
Fins were attached to limb girdles, which are supporting structures made a cartilage of bone.
These adaptations launched the adaptive radiation of the class Chondrichthyes: the sharks, rays, and skates.

17.   Bony Fishes
Ancient fishes evolved skeletons made of hard, calcified tissue called true bone.
Ray-finned fishes are aquatic vertebrates with skeletons of true bone; most have paired fines, scales, and gills.
Lobe-finned fishes are a different group of bony fishes that evolved fleshy fins supported by larger, more substantial bones.

18. Amphibians
The word amphibians means “double life”, referring to the fact that these animals live in water as larvae but on land as adults.
Several fossils indicate that various lines of lobe-finned fishes evolved sturdier and sturdier appendages, which resembled the limbs of tetra pods.
Early amphibians evolved ways to breathe air and protect themselves from drying out.

19. Reptiles
Reptiles, which evolved from ancient amphibians, were the first vertebrates to evolve adaptations to drier conditions
Dinosaurs lived in the Triassic and Jurassic period, and lived all over the world.
About 66 million years ago, a worldwide mass extinction occurred at the end of the Cretaceous Period.

20. Birds
Birds are reptiles that regulate their internal body temperature.
Recent fossil discoveries strongly support the hypothesis that birds evolved from a group of dinosaurs.
Modern birds by themselves, the traditional class Aves, from a clade within the clade containing dinosaurs.

21. Mammals
Characteristics unique to mammals include mammary glands in females, which produce milk to nourish you, and hair.
Mammals breathe air, have four-chambered hearts, and regulate their internal body temperature.
After birth, most placental mammals care for their young and nurse them to provide nourishment

22. 26.3 Primate Evolution

23. What Is a Primate?
Primates, including lemurs, monkeys, and apes, share several adaptations for a life spent in trees.
In general, a primate is a mammal that has relatively long fingers and toes with nails instead of claws, arms that can rotate around shoulder joints, a strong clavicle, binocular vision and a well-developed cerebrum.

24. Fingers, Toes, and Shoulders
Primates typically have 5 flexible fingers and toes on each hand or foot that can curl to grip objects firmly and precisely.
This enables many primates to run along tree limbs and swing from branch to branch with ease.
In addition, most primates have thumbs and big toes that can move against the other digits.

25. Binocular vision
Many primates have a broad face, so both eyes face forward with overlapping fields to view.
Binocular vision is the ability to combine visual images from eyes, providing depth perception and a three-dimensional view of the world.
This comes in handy for judging the locations of tree branches, from which many primates swing.

26. Evolution of Primates
Human and other primates evolved from a common ancestor that lived more than 65 million years ago
Primates in one of these groups look very little like typical monkeys

27. Tarsiers and Anthropoids
Anthropoids or humanlike primates, include monkeys, great apes, and humans.
New world monkeys also have a long, prehensile tail that can coil tightly enough around a branch to serve as a “fifth hand.”
Great apes, also called hominoids, include gibbons, orangutans, gorillas, chimpanzees, and humans.

28. Hominine Evolution
Hominines led to humans, and include modern humans and all other species more closely related to us than to chimpanzees.
Hominines also evolved much larger brains.

29. New Findings and New Questions
Since the 1990’s, new discoveries in Africa have doubled the number of known hominine species.
Hominine fossils date back to 7 million years.
There are various hypotheses on how these hominines relate to humans.

30. Relatives versus Ancestors
All hominine species relate to modern humans, but not all are human ancestors.
Distinguishing relatives from ancestors in the hominine family is an ongoing challenge.

31. The oldest hominine?
In 2002, paleontologists in central Africa discovered a skull 7 million years old.
This fossil is called Sahelanthropus.
Scientists are still debating whether this fossil represents a hominine.

32. Australopithecus
This type of hominines lived from about 4 million to about 1.5 million years ago.
Lucy, is a female skeleton discovered in 1974, which lived about 3.2 million years go.
In 2006, an Ethiopian researcher announced the discovery of some incredibly well preserved 3.3 million year old fossils of a very young female hominine.

33. The Road to Modern Humans
Hominines lived millions of years before modern humans.
Many species in our genus existed before our species, Homo sapiens, appeared; furthermore, at least three other Homo species existed at the same time as early humans.