Lecture 8: Consumers & Vertebrate Evolution PDF

Lecture 8: Consumers & Vertebrate Evolution Chapters 32, 34  Consumers / Heterotrophs Consumers are organisms that depend on other organisms for food. They take in organic molecules by essentially “eating” ingesting other living things. Consumers are also called...

Lecture 8: Consumers & Vertebrate Evolution Chapters 32, 34  Consumers / Heterotrophs Consumers are organisms that depend on other organisms for food. They take in organic molecules by essentially “eating” ingesting other living things. Consumers are also called heterotrophs. – They include all animals and fungi (fungi don't really “eat”; they absorb nutrients from other organisms; will discuss fungi in next lecture). – They also include many bacteria & protists – (even a few plants, such as the pitcher plant. Pitcher plants make their own food through photosynthesis & they also trap and eat insects. Pitcher plants are carnivorous plants that live in areas with low soil nutrients, ie low nitrogen soils) Heterotrophs are classified by what they eat: o Herbivores consume producers such as plants or algae. They link producers and other consumers. Examples include deer, rabbits, and mice. o Carnivores consume animals. Carnivores that are unable to digest plants and must eat only animals are called obligate carnivores. Other carnivores can digest plants but do not commonly eat them. Examples include lions, polar bears, & hawks. o Omnivores consume both plants and animals. They include humans, pigs, brown bears, crows, and some species of fish.  Protist Consumers - Ingestive Protists Are mostly Unicellular (single-celled) Are Heterotrophs - usually motile protists that feed by phagocytosis, though there are numerous exceptions. Can be classified into groups according to their mode of locomotion: - Pseudopodia (ex. Amoeba) - Cilia (Ciliates, ex. Paramecium) - Flagella (Flagellates, ex. Euglena) Phagocytosis: cellular uptake of molecules by the formation of a vesicle formed by the plasma membrane  Protist Consumers are classified primarily by their means of locomotion AMOEBAS: Unicellular, no cell wall have lobe-shaped, pseudopodia – Pseudopod: a temporary extension of an amoeboid cell that is used for locomotion (and feeding) Are commonly found in soil as well as freshwater and marine environments CILIATES: large varied group of protists. Are named for their use of cilia to move and feed (ex Paramecium) FLAGELLATES: diverse group that includes: heterotrophs, photosynthetic autotrophs, mixotrophs (they can do either) and pathogenic parasites Example: Euglena MIXOTROPHIC: autotrophic when sunlight available - they can become heterotrophic in absence of light Protist Consumers Soil protists: Heterotrophs: Phagotropy & Saprotrophs Parasites Symbionts  Kingdom Animalia Characteristics of ALL animals 1. Eukaryotic cells with no cell wall 2. Multicellular & have an extracellular matrix (structures on the outside of cell) that help bind cells together (gives added support and strength, ex. collagen) 3. Heterotrophic (ingest their food & then use enzymes to digest it within their bodies)  Kingdom Animalia Characteristics of MOST animals 4. Extensive cell specialization Cells are specialized to perform specific functions (ex. muscle & nerve cells) Groups of cells organized into tissues, organs, organ systems 5. Animals are motile (at least during one part of their lives) 6. Respond quickly and appropriately to changes in the environment (nervous and muscle tissue unique to animals) 7. Most animals reproduce sexually (some asexually)  Animal Diversity: 9 Phyla, most are invertebrates oldest most recent Jellyfish group Round worms Flat worms Sponges INVERTEBRATES: Animals lacking backbones (95% of Head = cephalized known animal species) The earliest animals evolved from colonial aquatic protist more than 600 million years ago.  Kingdom Animalia Animal Body Plan Segmentation The division of animal body plans into a series of repetitive segments. Advantages: Compartmentalization. Segmentation also allows for specialization with respect to bodily regions.  Kingdom Animalia Animal Body Plan Appendages External body parts, that protrude from an organism's body (in vertebrate biology, an example would be a vertebrate's limbs). Jointed appendages allow the animal much greater flexibility and range of movement.  Kingdom Animalia Cephalization An evolutionary trend toward the concentration of sensory equipment at the anterior end of the body (having a head) Evolutionary advantages: Development of brain Concentration of sense organs at the front of the body & close proximity of the mouth to the sense organs helps an animal rapidly sense food and Whiskers threats allows animals to communicate more effectively. o The facial features of cephalized animals can be used to express emotions and communicate with other animals. Electroreceptors Phylum Chordata The Chordates Chordates are named for a skeletal structure, the notochord, present in all chordate embryos as well as in some adults. Phylum Chordata The Cordate Body Plan 1. Notochord Longitudinal, flexible rod located between the digestive tube and the nerve cord. Provides skeletal support 2. Dorsal, hollow nerve chord Nerve cord of a chordate embryo develops into the central nervous system. 3. Pharyngeal slits In primitive chordates: Function in suspension feeding ad gas exchange (gill slits). In vertebrate fishes, the pharyngeal slits are modified into gill supports, and in jawed fishes, into jaw supports. In tetrapods, the slits are modified into components of the ear 4. Muscular, post-anal tail Tail that extends posterior to the anus (can be reduced during development)  Phylum CHORDATA MAIN GROUPS Lancelets - Invertebrates - Have all 4 chordate characteristics Tunicates: - Invertebrates - show the classic chordate characteristics only in their larval stage. Tunicates Lancelets Vertebrates (chordate animals that have a *BACKBONE) internal skeleton, notochord replaced with vertebral column in adults. Phylum Chordata / Invertebrates 1. Lancelets: The most basal (earliest- diverging) group of living chordates. Are the only group of chordate that retains all chordate characteristics as adults. Small fishlike animals that are generally less than 5 cm in length they burrow in gravel or sand with just the head exposed. Are suspension-feeders - water is driven into the mouth and pharynx Phylum Chordata / Invertebrates 2. Tunicates Tunicates, commonly called sea squirts, are a group of marine animals that spend most of their lives attached to docks, rocks or the undersides of boats. They are marine filter feeders with a water- filled, sac-like body structure with openings, through which they draw in and expel water The chordate characters of tunicates are most apparent during their larval stages. Adults only retain gill slits The Vertebrates Vertebrate: a chordate animal with a backbone or * vertebral column. *In some lineages, derived traits have been lost over time or occur in reduced form; lampreys, for example, are vertebrates with reduced vertebrae. Subphylum Vertebrata: The Jawless Vertebrates 3. The Jawless Fish: Hagfish The most basal group are the hagfishes (most primitive vertebrate) Have a skull made out of cartilage, but they lack jaws and vertebrae. they do not possess vertebral elements surrounding the dorsal nerve cord Marine, bottom dwelling scavengers.  Lancelets & Lampreys: tunicates vertebrates without jaws 4. The Jawless Fish: Lampreys Have rudimentary vertebrae (cartilaginous structures arranged above the notochord - not cartilaginous vertebrae bone). Most are parasitic and feed by clamping their round, jawless mouth onto the flank of a live fish. Cartilaginous skeleton They use their rasping tongue to penetrate the skin of the fish and ingest the fish’s blood. Subphylum Vertebrata 5. Jawed Vertebrates Subphylum Vertebrata Cartilage Fish - Evolution of Mineralized Skeletons A bony skeleton was a relatively late development in the history of vertebrates. The vertebrate skeleton evolved initially as a structure made of unmineralized cartilage. Cartilage in this group of animals can be mineralized with calcium for added support. This mineralization is hypothesized to have been associated with a transition in feeding mechanism. dental elements: first mineralized structure in vertebrate. Were an adaptation that may have allowed these animal to become scavengers and predators. Subphylum Vertebrata – Jawed Vertebrates Shark, Skates and Rays = Jawed fish with cartilaginous skeleton Have a skeleton primarily composed of cartilage. The cartilage can be mineralized with calcium for support. Includes sharks, rays and skates Subphylum Vertebrata – Bony Fish Bony fish, divided into 2 groups, 1st group: 6. Ray-finned fish Os = bone in French Subphylum Vertebrata – Bony Fish 6. Ray-finned fish Named for the bony rays that support their fins. Have an ossified endoskeleton with a hard matrix of calcium phosphate. All bony fishes use gills to breathe. Most aquatic bony fish possess a swim bladder that allows them to control their buoyancy. ancient vertebrate lineage had air air-filled sacs connected to the back of their throats that could be used for breathing air (i.e., as lungs) or for buoyancy control. The air bladders of many current ray-finned fish no longer connect to their throats, and so they are not able to breathe air. In these ray-fins, the air bladder evolved into the swim bladder mainly for buoyancy control. The swim bladder is believed to be homologous to the lungs of lungfish and the lungs of land vertebrates. Subphylum Vertebrata – Bony Fish Bony fish, group 2: 7. Lobe-Fined Fishes Lobed Ray-Finned Subphylum Vertebrata – Bony Fish 7. Lobe-Fined Fishes: Their "lung" is a modified swim bladder, which in most fish is used for buoyancy in swimming, but in the lungfish also absorbs oxygen. Modern lungfish (Africa and South America) are able to survive when their pools dry up by burrowing into the mud and sealing themselves within a mucous-lined burrow. During this time, they breathe air through their swim bladder instead of through their gills and reduce their metabolic rate dramatically. Bones in fins surrounded by a thick layer of muscle, fins are round in shape & able to support weight  Phylum Chordata - review 1. Lancelets Invertebrate chordates 2. Tunicates 3. Jawless fish – hagfish (Jawless, no backbone) 4. Jawless fish – lamprey (Jawless, with rudimentary vertebrae) 5. Cartilaginous fish – Have JAWS 6. Ray finned fish – Bony fish 7. Lobe finned fish – Lobed Bony fish Movement towards land: Legs! Tetrapods – four feet *a legless amphibian, evolved from a legged ancestor. These types of amphibians burrow in soil. In some lineages, derived traits have been lost over time or occur in reduced form; hagfishes and lampreys, for example, are vertebrates with reduced vertebrae.  The Movement to Land: Tetrapods 1st terrestrial vertebrates: Amphibians 1) Have lungs (adults) Lungs not very efficient Gas exchange thru skin (thin skin, desiccation is a problem, thus abundant in damp habitats) Must keep body moist 2) Developed skeletal structure that prevented the collapse of their bodies on land  Amphibians 3) Most Amphibians: external fertilization, female releases eggs in water, male releases sperm amid the eggs Eggs must remain in water or else they will dehydrate The Movement to Land: Tetrapods Reptiles: 1) Lungs 2) Endoskeleton (bones) Have scales that create a waterproof barrier (thick skin /scales (contains keratin) – have lungs) 3) Ectothermic 4) Internal fertilization - Modification where sperm can be deposited directly within female – remain in her No longer necessary to return to water to reproduce! Became completely independent of water with the formation of the amniotic egg (shelled egg)  Overview: Movement to land Amphibians: Lungs (gas exchange), endoskeleton, BUT need water for fertilization (limits range of movement) Reptiles: fertilization internal and great advantage: terrestrially adapted egg - amniotic egg!! Amniotic egg has a shell that retain water can be laid on land! adaptations to living on land.  Amniotic Egg A terrestrially adapted egg 1) Have amnion that 2) Allantois: collects wastes protects embryo (in a fluid 3) Yolk sac: nutrients (food) filled sac) from injury and 4) Chorion: gas exchange dehydration. Shell: tough, albumin, or egg impermeable to water white, provides the embryo with but permeable to O 2 water and and CO2 protein.  Amniotes are tetrapods that have a terrestrially adapted egg Amniotes include reptiles (includes birds) and mammas Birds are archosaurs (like crocodilians), but almost all features of their anatomy are modified and adapted for flight  Birds Lungs, Endoskeleton Have wings & feathers (to keep birds warm; endothermic, enable flight) Reproduction: Internal fertilization Birds also produce amniotic eggs  Drawbacks of Amniotic Egg Insufficient protection from predators ! Cannot survive drastic environmental changes  Amniotes Fish with Amniotes: land-living bones vertebrates, which have an amnion around developing embryo Types of Amniotic Animals: 1. Reptiles: amniotic egg, shell leathery (more flexible) 2. Birds: amniotic egg, bird shell inflexible (contain calcium carbonate) 3. Mammals: amnion, No shell  Mammals Three Groups of Mammals: Amniotes with mammary 1) Monotremes glands (secrete milk), hair, 2) Marsupials endothermic, specialized 3) Placental mammals teeth, enlarged skull Fertilization is internal  Monotremes ancestral mammals – Are a small group of egg-laying mammals consisting of echidnas and the platypus (Australia & New Guinea) – Lay eggs (characteristic retained from their reptilian ancestors) & mothers incubate eggs Lack placenta – Have hair & produce milk Echidna: After the egg hatches the young echidna, sucks milk from the pores in the mother’s pouch (they have no nipples)  Marsupials: opossums, kangaroos, and koalas The marsupials have internal development of the young. Embryo develops within a placenta in the mother’s uterus The young are born prematurely and must be reared in pouches. In the pouch they attach to a nipple and stay there until they are able to forge for themselves. Found in Australia and South Africa, only marsupial in North America is the opossum.  Placental Mammals (eutherians) Compared with marsupials, eutherians have a more complex placenta* In the placental mammals the membranes found in the egg have been modified. The embryo is still surrounded by an amnion filled with amniotic fluid. The allantois and yolk sac becomes the umbilical cord, providing a connection through which food reaches the fetus, and wastes are removed. Together with part of the chorion, these membranes make up the placenta, which physically attaches the embryo to the uterine wall of its mother. It is across the placenta that air, food, and wastes must be transferred * Young eutherians complete their embryonic development within uterus, joined to mother by placenta