8/25/ Opening Questions: Are you an animal? What traits do you share with a jellyfish? Chapter 10 Biodiversity 3: Animals

Transcription

1 Chapter 10 Biodiversity 3: Animals 10.1 Animals are consumers 10.2 Sponges and cnidarians 10.3 Three phyla of worms 10.4 Mollusks 10.5 Arthropods 10.6 Echinoderms 10.7 Vertebrates 10.8 Fishes 10.9 Amphibians and reptiles Mammals Humans evolved from primates 10.1 Opening Questions: Are you an animal? What traits do you share with a jellyfish? What traits do you share with an earthworm? What traits do you share with a chimpanzee? 10.1 All animals eat other organisms. Animals are heterotrophs. They obtain food from their environment. Heterotrophs are also called consumers. In contrast, autotrophs are organisms that make their own food (like plants). Autotrophs are also called producers Animals are heterotrophs that evolved from colonial protists. Biologists hypothesize that the first animal evolved around 600 million years ago. This hypothetical organism may resemble the colonies of protists that evolved into the first animals All animals share a set of common features Today there are 9 major animal phyla. Note that the vast majority of animals are invertebrates, animals without backbones. 1

2 10.2 Opening Questions: Plant, animal, or mineral? Take a good look at the image. Is this a plant, an animal, or a rock? Design a test that you could perform that would allow you to make a definitive conclusion Sponges and cnidarians are animals that have unusual body features. Both groups are mostly marine. Sponges lack body symmetry and tissues. Cnidarians are radially symmetrical; they have tissues and stinging cells Sponges have the longest evolutionary history of all animals. Characteristics of sponges: 1. Asymmetrical shape 2. Lack tissues 3. Sessile In a sponge, the lack of tissues means that every cell must be in contact with the environment A gallery of sponges Freshwater sponge Orange elephant ear sponge Branching vase sponge 10.2 Cnidarians include sea anemones, hydras, corals, and jellies. Characteristics of cnidarians: 1. Radial symmetry 2. Cells organized into tissues 3. Stinging cells 4. Two distinct body forms: 10.2 A gallery of cnidarians Sea wasp Sea anemone A stationary polyp like this sea anemone A floating medusa like this jelly Gray hydra Boulder brain coral 2

3 10.3 Opening Questions: True or false? Explain your choice: True or false: Cnidarians, including jellies, may predate dinosaurs by some 200 million years. True or false: Most corals obtain the majority of their energy from photosynthetic unicellular algae that live within the coral s tissue. True or false: Jellies can sting you even after they are dead The animal kingdom includes three phyla of worms with separate lineages. Flatworms, annelids, and roundworms share similar body shape, but vary considerably. Each phylum has its own evolutionary heritage and distinctive features Flatworms lack a digestive tract A gallery of flatworms Characteristics of flatworms: 1. Bilateral symmetry 2. Gastrovascular cavity 3. No true body cavity 4. Eyespots 5. Sex organs 6. Some are parasites Tapeworm Fluke A planarian Marine fascia flatworm 10.3 Annelids display a key evolutionary adaptation: segmentation. Characteristics of annelids: 1. Bilateral symmetry 2. Complete digestive tract 3. Closed circulatory system 4. Body cavity 5. Body segments 10.3 A gallery of annelids Earthworm Leech Polychaetes 3

4 10.3 Roundworms, or nematodes, have cylindrical bodies tapered at both ends. Characteristics of roundworms: 1. Bilateral symmetry 2. Complete digestive tract 3. No body segments 10.4 Opening Questions: Can you think like a zoologist? Zoology (from the Greek zoon, animal + logos, to study) is the study of animals including their growth, development, function, distribution, and origin. What types of questions does a zoologist ask? Heartworm Soil nematode Thinking like a zoologist, describe an observation you have made about an animal? Generate a question and a hypothesis. How might you test your hypothesis? 10.4 Mollusks are a diverse phylum. Mollusks are a phylum of softbodied animals, many of which are protected by a hard shell. Snails and slugs, oysters and clams, octopuses and squids are all mollusks Mollusks all have a similar body plan and many have a hard shell. Characteristics of mollusks: 1. Bilateral symmetry 2. Three main parts: muscular foot, visceral mass, and mantle 3. Open circulatory system 4. External shell (most) 5. Gills (most) 6. Radula file-like organ Garden snail 10.4 A gallery of mollusks 10.5 Opening Questions: Heads and tails? Gastropods (snails and slugs) Banana slug Bivalves (clams, mussels, and oysters) Bay scallop Cephalopods (squid and octopi) European squid All animals, besides the cnidarians, exhibit bilateral symmetry: they can be split into roughly mirrored halves by slicing down the midline. However, the precise evolutionary importance of bilateral symmetry is still an area of active research. Identify at least one possible advantage of having bilateral symmetry, including having a head and a tail. Be prepared to explain your reasoning. 4

5 10.5 The arthropods are by far the most numerous and diverse phylum of animals. In terms of numbers of individuals and species, arthropods are the most successful animal phylum. Common groups of arthropods include: Arachnids (e.g., spiders) Centipedes and millipedes Crustaceans (e.g., lobsters) Insects (e.g., butterflies) 10.5 Arthropods are tremendously diverse, but share some key features. Characteristics of arthropods: 1. Bilateral symmetry 2. Body segments: Head, thorax, and abdomen 3. Hard exoskeleton An American lobster 10.5 Arachnids are a group of eight-legged arthropods. Arachnids include spiders, scorpions, ticks, and mites. Most are terrestrial carnivores. Tarantula 10.5 Millipedes and centipedes have obviously segmented bodies. The two groups can be distinguished by the number of legs on each body segment. All are land dwelling. Yellow desert scorpion Wood tick Atlantic horseshoe crab Centipede (one pair of legs per segment) Millipede (two pairs of legs per segment) 10.5 Crustaceans are common arthropods in marine and freshwater habitats. Many of them (shrimp, lobster, crabs, etc.) are valuable food crops Insects, by far, outnumber all other animals combined. Most have easily recognizable segments (head, thorax, and abdomen), three pairs of legs, and one pair of antennae. Goosenecked barnacles Common rough woodlouse Brown crab 5

6 10.6 Opening Questions: True or false? Explain your choice: True or false: There more kinds of insects on Earth than any other kind of animal. True or false: The blood of lobsters is blue. True or false: A flea can leap up to 38 times its body weight and at an acceleration of around 100 g-force Echinoderms are a sister phylum to the chordates. Echinoderms share an evolutionary branch with chordates (which include vertebrates). All species are marine. Echinoderms include: sea stars, sea urchins, sea cucumbers, and sand dollars Echinoderms are the phylum most closely related to our own. Characteristics of echinoderms: 1. Larval bilateral symmetry Often radially symmetrical as adults 2. Water vascular system and tube feet 3. Endoskeleton 4. Spiny surface 5. Tube feet 6. Mouth 7. Regeneration 10.6 A gallery of echinoderms Red sea urchin Bennett s feather star Brittle star Donkey dung sea cucumber 10.6 We share an evolutionary kinship with echinoderms. Although an adult sea star looks nothing like an adult human, our lineages share some important similarities in embryo development Opening Questions: Are you feeling spineless? Most of the chordates are also vertebrates (have a backbone). What are all the similarities and differences you can think of among these vertebrate groups? Fishes Amphibians Reptiles Mammals 6

7 10.7 Vertebrates (animals with backbones) belong to the chordate phylum. Common groups of chordates include: Lancelets Tunicates Fishes Amphibians Reptiles Mammals 10.7 All chordates are recognized by four features. These four features are apparent in all chordate embryos, but may not be clear in the adult There are two chordate groups that are classified as invertebrates. Lancelets are small animals that capture food by filtering water through their mouths Most chordates are vertebrates. Vertebrates have an endoskeleton (an internal skeleton) that includes a backbone and a skull. Tunicates are sessile and feed by filtering seawater Novel features distinguish each of the main groups of chordates Opening Questions: Mammal or fish? At first glance, there are some similarities among dolphins and sharks, even though a shark is a fish and a dolphin is a mammal. This can be especially true in grainy beach photos! Why might the overall body structure of the shark and the dolphin be so similar? 7

8 10.8 The first vertebrates to evolve were fishes. The first fish evolved around 540 mya. The fish lineage was the first to evolve jaws. Modern fishes include several lineages: Hagfish Lampreys Cartilaginous fishes Bony fishes 10.8 There are two modern fish lineages that lack a jaw. Hagfishes have a skull but lack a recognizable backbone. Lampreys have a skull and backbone, but they lack a jaw The first vertebrates with jaws were cartilaginous fishes. Cartilaginous fishes have flexible skeletons made of cartilage and must constantly move to keep water flowing through the gills. Most are marine predators There are more species of bony fishes than any other group of vertebrates. Bony fishes were the first group to have internal skeletons reinforced with calcium. They also have a swim bladder to maintain buoyancy, and an operculum that circulates water over the gills A gallery of bony fishes 10.8 The lobe-finned fishes are an evolutionary branch of the bony fishes. Lobe-finned fishes have muscular fins supported by rod-shaped bones that are homologous to amphibian limb bones. Rainbow trout Spotfin butterflyfish The lobe-fins include the lungfishes. Chevron barracuda Thorny seahorse 8

9 10.9 Opening Questions: Name the phyla. On a trip to the ocean you spot the following organisms. To which phyla does each organism belong? Orange elephant ear sponge (Agelas clathrodes) Bay scallop (Argopecten irradians) Banana slug (Ariolimax californicus) Southern stingray (Dasyatis americana) Brain coral (Colpophyllia natans) Brittle star (Ophiothrix fragilis) Tunicates (Atriolum robustum) Goosenecked barnacles (Lepas pectinata) 10.9 Amphibians and reptiles have four limbs and were the first to occupy land. All terrestrial vertebrates are tetrapods, animals with four limbs. Amphibians were the first tetrapods. They were followed by the evolution of reptiles (including birds) Amphibians live on land, but must reproduce in water. Amphibians exhibit a blend of aquatic and terrestrial adaptations. Aquatic adaptations: Eggs that lack shells Tadpole stage has gills Terrestrial adaptations: Adult has lungs Musculoskeletal system with four limbs Moist skin 10.9 A gallery of amphibians Frogs have powerful hind legs that allow hopping. Toads live entirely on land. Caecilians superficially resemble earthworms or snakes. Salamanders can be either aquatic or terrestrial Reptiles, including birds, can complete their entire life cycle on land. Reptiles (and mammals) are amniotes, animals that develop inside a fluid-filled amniotic egg. One hypothesis places reptiles into four groups, although this a subject of debate Four major reptile groups Turtles Dinosaurs and birds Crocodilians Lizards and snakes 9

10 10.9 Fossils suggest that birds are part of a dinosaur group called theropods. Birds display many adaptations for flight Opening Questions: Tastes like dino? Identify three similarities and three differences between modern birds (such as a chicken) and pre-avian dinosaurs Mammals are tetrapods that have hair and produce milk in mammary glands. After the dinosaur mass extinction 65 mya, mammals rapidly diversified. Modern mammals can be divided into three groups: Monotremes Marsupials Eutherians Monotremes are the only surviving egg-laying mammals. The only modern monotremes are the duck-billed platypus and four species of echidna. Short-beaked echidna The duck-billed platypus Marsupials mature in pouches. After a brief pregnancy, a marsupial gives birth to a tiny embryonic offspring that completes its development in its mother s pouch, attached to a nipple Most marsupials are found in Australia. Australia split off from the other continents around 60 mya. Isolated from the evolution of later groups of mammals, marsupials diversified extensively. Eastern gray kangaroo with offspring 10

11 10.10 Eutherian offspring are born fully developed after maturing with a placenta. The placenta of a eutherian connects the developing fetus to the uterine wall. This allows nutrient uptake, waste elimination, and gas exchange via the mother s blood supply. Many mammals are born encased in an amniotic sac A gallery of eutherians Most mammals, such as this dog, are terrestrial. There are about 1,000 species of bats. There are about 80 species of cetaceans, or aquatic mammals Opening Questions: When did we arrive? Imagine the history of life on Earth compressed into a single 24-hour day. The clock starts ticking at 5,000 mya and goes to the present (hour 24:midnight). 18:00 1,250 mya 12 Noon 2,500 mya 06:00 3,750 mya Where do humans sit on the tree of life on Earth? Humans are in the phylum of chordates and are mammals who belong to the order of primates. pg 246 At what time would you put the appearance of our species, Homo sapiens? As a group, primates share some distinctive characteristics. Primate characteristics: Large brains Binocular vision Limber joints, limbs, and digits Complex behaviors Extended parental care Humans evolved from ancestral primates several million years ago. Fossil and DNA evidence suggest that the human lineage, the hominins, split from other primates around 5 to 7 million years ago. Many lineages evolved, but only one, ours, has survived. Primates are further divided into the nonanthropoids and the anthropoids. 11

12 10.11 Highlights in the timeline of human evolution Many of the features that distinguish modern humans appeared long before our species, Homo sapiens. ~ 4.0 to 2.9 mya: Australopithecus afarensis The earliest known hominin to display a key human trait: bipedalism. Found in Africa. Fossil hominin skeleton known as Lucy Highlights in the timeline of human evolution ~ 2.4 to 1.7 mya: Homo habilis Intermediate in brain size with evidence for tool use. The oldest known member of our own genus. ~ 1.8 to 1.3 mya: Homo erectus The first hominin species known to have migrated out of Africa to other continents Highlights in the timeline of human evolution ~ 350,000 to 30,000 years ago: Homo neanderthalensis DNA analysis suggests that Neanderthals and H. sapiens were not direct relatives but most likely interbred. ~ 200,000 years ago to present: Homo sapiens From Africa, our species spread into Asia (approximately 50,000 years ago), and then to Europe and Australia A few important points about human evolution Humans did not evolve from chimps. We share a common ancestor. Human evolution did not proceed from one species to the next. Human evolution is not an orderly procession and many species coexisted. Key human features did not evolve all at once. Features, such as upright posture and speech, evolved separately and at different times When did we arrive? Imagine the history of life on Earth compressed into a single 24-hour day. The clock starts ticking at 5,000 mya and goes to the present (hour 24:midnight). 18:00 1,250 mya 12 Noon 2,500 mya Genus Homo arrives at just around 34 seconds before midnight (~ 2 mya). Homo sapiens arrives less than 4 seconds before midnight (~ 0.2 mya)! 06:00 3,750 mya 12