Chapter 23 The Animal Kingdom

1. Chapter 23The Animal Kingdom

2. General Features of Animals • All animals are multicellular heterotrophs • They are diverse in form • Invertebrates are animal species that lack a backbone • Vertebrates have a backbone (about 1% of Kingdom Animalia) • No cell walls • Active Movement • Sexual Reproduction • Embryonic Development

3. Evolution • The first multicellular animals evolved about 600 million years ago. • From humble beginnings, they diversified into many habitats.

4. Evolutionary Innovations • We will learn about animal diversity by examining a series of nine key evolutionary innovations, each exemplified by a major phylum.

5. The Simplest Animals • The simplest animals, members of the phylum Porifera • Members of phylum Porifera include sponges • Characteristics of sponges • Lack symmetry • Not organized into tissues

6. Sponges • Sponges are perforated by tiny holes (where name of phylum comes from • They have unique flagellated cells that line the body cavity of the sponge • The flagella on the cells will draw water through the sponge and throughout the body cavity • Any food particles in the water will be trapped and later ingested

7. Phylum Cnidaria • Phylum Cnidaria consists of jellyfish, sea anemones, sea coral and hyroids • Unlike sponges, they have symmetry and tissues • Able to undergo extracellular digestion, where digestion takes place inside a body cavity • Cnidarians have two true tissue layers: ectoderm and endoderm • They have radial symmetry and a nerve net to provide sensory input.

8. Symmetry • Symmetrical objects have similar parts that are arranged in a similar manner • Three types of symmetry • Asymmetry – no pattern in parts • Radial Symmetry – when a body is constructed around a central axis • Bilateral symmetry – is when an animal is constructed with equivalent parts on both sides of a plane, includes a definite head end, known as cephalization

9. Phylum Platyhelminthes • In phylum Platyhelminthes (flatworms), they have bilateral symmetry, so they have cephalization • Also have three embryonic layers, the outer ectoderm, the inner endoderm, and a third layer, the mesoderm, which forms between the ectoderm and the endoderm • The ectoderm forms into the outer covering of the body and the nervous system • The digestive and intestines develop from the endoderm • The skeleton and muscle form from the mesoderm • They do not have a body cavity, making them acoelomates

10. Flatworms • Have a simple body design, but do have a definite head and organs • Most species are parasitic, occurring within the bodies of many other kinds of animals • Have an incomplete gut, with only one opening • They cannot feed, digest, and eliminate waste simultaneously • Lack a circulatory system • Undergo diffusion of oxygen • Many are hermaphroditic, with each individual containing both male and female parts

11. Body Cavity • A key transition in the evolution of the animal body was that of a body cavity. • All bilaterally symmetrical animals other than solid worms have a cavity within their body • Important for body design for: • Circulation – fluids can move within the body cavity, permitting the rapid passage of materials from one part of body to another • Movement – Fluid in cavity makes animal’s body rigid, making it harder for muscle contractions • Organ Function – Body organs can function without body being deformed by surrounding muscles

12. Body Cavities • Three basic kinds of body plans found in bilaterally symmetrical animals • Acoelomates – have no body cavity • Pseudocoelomates – have a body cavity called the pseudocoel located between the mesoderm and endoderm develops entirely • Coelomates – has a fluid-filled body cavity not between the endoderm and mesoderm, but rather entirely within the mesoderm, coelom • Gut is suspended, along with other organ systems

13. Phylum Nematoda • In phylum Nematoda, they are pseudocoelomates, the first evolutionary phylum to have an internal body cavity. • Includes nematodes, ellworms and rotifers • Nematodes mouth is often equipped with piercing organs, and the food will pass through the mouth as a result of the sucking action of a muscular chamber, known as the pharynx. After passing the pharynx food continues through the digestive tract and is eliminated through the anus

14. Phylum Mollusca • Phylum Mollusca have a coelom, which is more functional than animals without coeloms. • This is because of primary induction, where one of the three primary tissues (endoderm, mesoderm, and ectoderm) interact with one another • Only coelomate without a segmented body • Most have a radula, a rasping, tongue-like organ • Used to scrape algae off rocks

15. Phylum Mollusca • Mollusks are divided into with outwardly different body plans • The three different classes of mollusks • Gastropods – include snails and slugs, use a muscular foot to crawl, their mantle secretes a single, hard protective shell • Bivalves – include clams, oysters and scallops, secrete a two-part shell, with a hinge • Cephalopods – include octopuses and squids, have a modified mantle cavity to create a jet propulsion system to propel them through water

16. Phylum Annelida • In this phylum, their key evolutionary trait is segmentation, where the building of a body is from a series of similar segments • Includes: Earthworms, brittle worms • In phylum Annelida, there segmentation are nearly identical segments • The advantage of segmentation is hat segments are able to have different functions, such as reproduction, feeding

17. Phylum Annelida • Annelida organization is simply basic body structure of Annelida: is a tube within a tube; the digestive tract is a tube suspended within the coelom • Repeated segments: each segment has digestive, excretory, and locomotor organs • Specialized segments: sensory organs that are sensitive to light • Connections: circulatory and nervous connections to each segment

18. Phylum Arthropoda • This phylum includes insects, crabs, shrimp lobsters, crayfish, water fleas • Their evolutionary adaption include jointed appendages and exoskeleton • Their exoskeleton is a rigid external skeleton made of chitin and provides places for muscle attachment • Helps protect against predators and slow water loss

19. Phylum Arthropoda • Arthropods that lack jaws, also known as mandibles are called chelicerates. • These include spiders, mites, scorpions • Those with mandibles that were formed through the modification of anterior appendages are known as mandibulates. • This group includes crustaceans, insects, centipedes and millipedes

20. Mandibulates • Crustaceans – large, diverse group of primary aquatic animals. • Most have two pair of antennae, three pairs of chewing appendages, and various number of legs • Have compound eyes • Millipedes and Centipedes • Centipedes have one pair of legs on each segment • Millipedes have two pairs of legs on each segment

21. Mandibulates • Insects are the largest group of arthropods • They have three body sections • Head – very elaborate, with one pair of antennae and elaborate mouthparts and compound eyes • Thorax – has three segments as well, each of which have one pair of legs; most insects have two pairs of wings attached to the thorax • Abdomen – digestion takes place, and have excretion organ called Malpighian tubes

22. Embryonic Development • In coelomates, there are two different types of embryonic development • In mollusks, annelids, and arthropods, the mouth near the blastopore making it a protostome • Protostomes form in a cleave radially and are tightly packed

23. Embryonic Development • In echinoderms and chordates,the anus forms near the blastopore, making it a deuterostome • It forms through spiral cleavage

24. Phylum Echinodermata • In phylum Echinodermata include sea stars, sea urchins, sand dollars and sea cucumbers • Their key evolutionary developments include deuterostome development and endoskeleton • The endoskeleton is composed of hard calcium-rich plates just beneath a delicate skin • They have pentamerous (5-way) symmetry. • All members have a water vascular system which acts like a line of suction cups along radial canals to tube feet.

25. Phylum Chordata • Lancets, terrestrial vertebrates are included in this group • The major evolutionary innovation in this group is the notochord • In all of the 50 thousand species, there are four principal features • Notochord • Nerve Cord • Pharyngeal slits • Postanal Tail

26. Phylum Chordata • Notochord is a stiff, but flexible rod that forms beneath the nerve cord that acts to anchor internal muscles, permitting rapid body movements • Nerve cord is a single dorsal hollow nerve cord, which the nerves that reach the different parts of the body are attached • Pharyngeal slits are a series of slits behind the mouth into the pharynx ,which is a muscular tube the mouth to the digestive tract and windpipe • Postanal Tail is a tail that extends beyond the anus

27. Amniotic Egg • While amphibians were the first land animals, they are still largely tied to the water for reproduction and resupply body fluids. • One key step was the development of a waterproof skin. • The evolution of the amniotic egg expanded the success of vertebrates on land by allowing reproduction on land. • A series of specialized membranes function in gas exchange, waste storage, and energy storage for the developing embryo

28. Mammals • Hair traps body heat. • All mammal females supply nourishment to their offspring in the form of milk. • It is produced in special glands. • The Monotremes (platypus and echidna) actually lay eggs. • Marsupials begin development internally, but young are born are a very early stage and do most of their development in a pouch. • In placental mammals, embryos complete far more of their development in a special support structure, the placenta.