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Biology - Chapter 29 “Echinoderms and Invertebrate Chordates” Charles Page High School Stephen L. Cotton Section 29-1 Echinoderms OBJECTIVES: Relate the structure of echinoderms to essential life functions. Section 29-1 Echinoderms OBJECTIVES:

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biology chapter 29 echinoderms and invertebrate chordates

Biology - Chapter 29“Echinoderms and Invertebrate Chordates”

Charles Page High School

Stephen L. Cotton

section 29 1 echinoderms
Section 29-1Echinoderms
    • Relate the structure of echinoderms to essential life functions.
section 29 1 echinoderms3
Section 29-1Echinoderms
    • Describe the characteristics of the classes of echinoderms.
section 29 1 echinoderms4
Section 29-1Echinoderms
  • Phylum Echinodermata- starfish, sea urchins, sand dollars, etc.
    • echino- means spiny; dermis means skin
    • these are spiny-skinned animals
    • Cambrian period; 580 million yr.
section 29 1 echinoderms5
Section 29-1Echinoderms
  • In addition to having spiny skin, they are characterized by:
    • 5 part radial symmetry
    • internal skeleton
    • water vascular system
    • suction-cuplike structures called “tube feet”
section 29 1 echinoderms6
Section 29-1Echinoderms
  • The internal skeleton (or endoskeleton) is made up of hardened plates of calcium carbonate; often bumpy or spiny
  • water vascular system consists of an internal network of fluid-filled canals connected to the external appendages called tube feet
section 29 1 echinoderms7
Section 29-1Echinoderms
  • The water vascular system is essential for:
    • feeding; respiration; internal transport; elimination of wastes; and movement
  • Echinoderms have an internal skeleton like Chordates, and some similar development
section 29 1 echinoderms8
Section 29-1Echinoderms
  • Thus, some biologists feel that among invertebrates, echinoderms are most closely related to humans!
  • Echinoderms are somewhat “ugly”- however, they are very well adapted to life in the sea; have changed very little
section 29 1 echinoderms9
Section 29-1Echinoderms
  • Adult echinoderms have a body plan with five parts organized symmetrically around a center
    • neither anterior nor posterior end; no brain
    • but, they are two-sided
    • mouth side is the oral surface
section 29 1 echinoderms10
Section 29-1Echinoderms
  • Side opposite the mouth is the aboral surface
  • they have a unique system of internal tubes called a water vascular system
    • opens to the outside through a sieve-like structure called the madreporite
section 29 1 echinoderms11
Section 29-1Echinoderms
  • In starfish, the madreporite connects to a tube called the ring canal that forms a circle around the animal’s digestive system
    • Figure 29-3, page 639
    • from the ring canal, five radial canals extend into each body segment
section 29 1 echinoderms12
Section 29-1Echinoderms
  • Attached to each radial canal are hundreds of movable tube feet
    • this entire system acts like a series of living hydraulic pumps that can propel water in or out of the tube feet
    • can create a partial vacuum to hold on to what it is touching
section 29 1 echinoderms13
Section 29-1Echinoderms
  • Feeding-
    • carnivores, such as starfish, use their tube feet to pry open the shells of bivalve mollusks
      • then flips the stomach out of it’s mouth, pours out enzymes, and digests it’s prey in its own shell; then pulls the stomach back, leaving an empty shell
section 29 1 echinoderms14
Section 29-1Echinoderms
  • Herbivores, such as sea urchins, scrape algae from rocks by using their 5-part jaw
  • Filter feeders, such as sea lilies, basket stars, and some brittle stars, use tube feet on flexible arms to capture plankton that float by on ocean currents
section 29 1 echinoderms15
Section 29-1Echinoderms
  • Detritus feeders, such as sea cucumbers, move much like a bulldozer- taking in a mixture of sand and detritus
    • much like an earthworm, they digest the organic material and pass the sand grains out in their feces
section 29 1 echinoderms16
Section 29-1Echinoderms
  • Respiration- in most species, the thin-walled tissue of the tube feet forms the main respiratory surface
    • in some species, small outgrowths called skin gills also function in gas exchange
section 29 1 echinoderms17
Section 29-1Echinoderms
  • Internal transport- the functions of transporting oxygen, food, and wastes- which is normally done by a circulatory system, are shared by different systems in echinoderms
    • don’t really need a system for gases, because of gills and skin
section 29 1 echinoderms18
Section 29-1Echinoderms
  • The distribution of nutrients is performed primarily by the digestive glands and the fluid within the body cavity
  • Excretion- in almost all echinoderms, solid wastes are released through the anus (on the aboral surface) as feces
section 29 1 echinoderms19
Section 29-1Echinoderms
  • The nitrogen-containing cellular wastes are excreted primarily as ammonia
    • wastes seem to be excreted in many of the same places around the body in which gas exchange takes place- the tube feet and the skin gills
section 29 1 echinoderms20
Section 29-1Echinoderms
  • Response- since they have no head, they have primitive nervous systems
    • they do have scattered sensory cells to detect food
    • starfish also have up to 200 light-sensitive cells clustered in eyespots at the tip of each arm
section 29 1 echinoderms21
Section 29-1Echinoderms
  • However, they can do little more than tell whether it is light or dark
    • also may have statocysts for balance, telling them whether it is right side up
  • the spiny surface is not very good protection; good in some such as the crown-of-thorns starfish
section 29 1 echinoderms22
Section 29-1Echinoderms
  • Many predators have learned that if they turn these animals over, they can attack them through their unprotected underside
    • thus, many echinoderms hide during the day; active at night when most predators sleep
section 29 1 echinoderms23
Section 29-1Echinoderms
  • Movement- use tube feet and thin layers of muscle fibers attached to the plates of the endoskeleton to move
    • in sand dollars and sea urchins, the plates are fused together to form a rigid box that encloses the animal’s internal organs
section 29 1 echinoderms24
Section 29-1Echinoderms
  • In sea cucumbers, the plates are reduced to tiny vestiges inside a soft, muscular body wall. The loss of the plates makes the body of sea cucumbers very flexible
section 29 1 echinoderms25
Section 29-1Echinoderms
  • Reproduction- most echinoderms are either male or female, some are hermaphrodites
    • place the eggs and sperms in the water where fertilization takes place
    • the larvae have bilateral symmetry- very advanced
section 29 1 echinoderms26
Section 29-1Echinoderms
  • When the larvae mature and metamorphose into adults, they have radial symmetry
  • many starfish have incredible powers of regeneration
    • each piece can grow into a new animal as long as it contains a portion of the central part
section 29 1 echinoderms27
Section 29-1Echinoderms
  • Echinoderm Classes- 5 classes, although exact names not given
  • almost 6,000 species found in almost every ocean (salt water) in the world
    • no echinoderms have ever entered fresh water, and they cannot survive for long on land
section 29 1 echinoderms28
Section 29-1Echinoderms
  • 1. Starfish- this class contains the common starfish, which are also known as sea stars
    • some have more than 5 arms
    • Figure 29-7, page 642
    • carnivorous, preying upon the bivalves they encounter
section 29 1 echinoderms29
Section 29-1Echinoderms
  • 2. Brittle Stars- live in tropical seas, especially on coral reefs
    • look like common starfish, but longer more flexible arms- thus able to move much more rapid
    • protection by shedding one or more arms when attacked; are filter and detritus feeders
section 29 1 echinoderms30
Section 29-1Echinoderms
  • 3. Sea Urchins and Sand Dollars- includes disk-shaped sand dollars, oval heart urchins, and round sea urchins Fig. 29-8, p. 643
    • are grazers that eat large quantities of algae; may burrow into the sand or mud; may protect by long sharp spines
section 29 1 echinoderms31
Section 29-1Echinoderms
  • 4. Sea Cucumbers- look like warty moving pickles, with a mouth at one end and an anus at the other
    • Figure 29-9, page 644 top
    • most are detritus feeders
    • some produce a sticky material to “glue” a predator helpless
section 29 1 echinoderms32
Section 29-1Echinoderms
  • 5. Sea Lilies and Feather Stars- filter feeders, have 50 or more long feathery arms
    • the most ancient class of echinoderms; not common today, but once were widely distributed
    • sea lilies: sessile animals-p.644
section 29 1 echinoderms33
Section 29-1Echinoderms
  • How Do Echinoderms Fit Into the World?
    • Starfish are important carnivores, controlling other animal populations; a rise or fall in numbers affects other populations
section 29 1 echinoderms34
Section 29-1Echinoderms
  • For example, several years ago the coral-eating crown-of-thorns starfish suddenly appeared in great numbers in the Pacific Ocean
    • within a short period of time, they caused extensive damage to many coral reefs
section 29 1 echinoderms35
Section 29-1Echinoderms
  • In many coastal areas, sea urchins are important because they control distribution of algae
  • in various parts of the world, sea urchin eggs and sea cucumbers are considered delicacies by some people
section 29 1 echinoderms36
Section 29-1Echinoderms
  • Several chemicals from starfish and sea cucumbers are currently being studied as potential anti-cancer and anti-viral drugs
  • sea urchins have been helpful in embryolgy study, since they produce large eggs; fertilize externally; develop in sea water
section 29 2 invertebrate chordates
Section 29-2Invertebrate Chordates
    • Name and discuss the three distinguishing characteristics of chordates.
section 29 2 invertebrate chordates38
Section 29-2Invertebrate Chordates
    • Describe the two subphyla of invertebrate chordates.
section 29 2 invertebrate chordates39
Section 29-2Invertebrate Chordates
  • The phylum Chordata, to which fishes, frogs, birds, snakes, dogs, cows, and humans belong, will be in future chapters
    • most chordates are vertebrates, which means they have backbones, and are placed in the subphylum Vertebrata
section 29 2 invertebrate chordates40
Section 29-2Invertebrate Chordates
  • But, there are also invertebrate chordates- these are divided into two subphyla:
  • 1. the tunicates
  • 2. the lancelets
  • due to similar structures, the chordate vertebrates and invertebrates may have evolved from a common ancestor
section 29 2 invertebrate chordates41
Section 29-2Invertebrate Chordates
  • Chordates are animals that are characterized by a notochord, a hollow dorsal nerve cord, and pharyngeal (throat) slits
    • some chordates posses these characteristics as adults; others as only embryos; but all have them at some stage of life
section 29 2 invertebrate chordates42
Section 29-2Invertebrate Chordates
  • 1. Notochord- a long, flexible supporting rod that runs through at least part of the body, usually along the dorsal surface just beneath the nerve cord
    • most chordates only have this during the early part of embryonic life
section 29 2 invertebrate chordates43
Section 29-2Invertebrate Chordates
  • Vertebrates will replace the notochord quickly with the backbone
  • 2. The second chordate characteristic- the hollow dorsal nerve cord- runs along the dorsal surface just above the notochord
section 29 2 invertebrate chordates44
Section 29-2Invertebrate Chordates
  • In most chordates, the front end of this nerve cord develops into a large brain
    • nerves leave this cord at regular intervals along the length of the animal, and connect it’s internal organs, muscles, and sense organs
section 29 2 invertebrate chordates45
Section 29-2Invertebrate Chordates
  • 3. The third chordate characteristic- the pharyngeal slits- are paired structures in the pharyngeal (or throat) region of the body
    • in aquatic chordates such as lancelets and fishes, the pharyngeal slits are gill slits that connect with the outside
section 29 2 invertebrate chordates46
Section 29-2Invertebrate Chordates
  • In terrestrial chordates that use lungs for respiration, pharyngeal slits are present for only a brief time during the development of the embryo
    • they soon close up as the embryo develops- page 283
section 29 2 invertebrate chordates47
Section 29-2Invertebrate Chordates
  • In humans, pouches form in the pharyngeal region, but never open up to form slits
    • thus, some scientists consider the pharyngeal pouches, not slits, as the “true” chordate characteristic
section 29 2 invertebrate chordates48
Section 29-2Invertebrate Chordates
  • Tunicates- small marine chordates that eat plankton they filter from the water
    • name from a special body covering called the tunic
    • only the tadpole-shaped larvae have the notochord and dorsal nerve cord
section 29 2 invertebrate chordates49
Section 29-2Invertebrate Chordates
  • Examples of tunicates are the sea squirts Figure 29-11, page 646
    • adults are sessile, living as colonies attached to a solid surface; larvae are free swimming
section 29 2 invertebrate chordates50
Section 29-2Invertebrate Chordates
  • Lancelets- small fishlike creatures; live in sandy bottoms of shallow tropical oceans
    • unlike tunicates, the adult lancelets have a definite head; a mouth that opens into a long pharyngeal region with up to 100 pairs of gills
section 29 2 invertebrate chordates51
Section 29-2Invertebrate Chordates
  • Figure 29-12, page 646
    • feed by passing water through their pharynx, where food particles are caught in a sticky mucus; lack any jaws
    • have a primitive heart pumping blood through closed circulation
section 29 2 invertebrate chordates52
Section 29-2Invertebrate Chordates
  • Lancelet’s muscles are organized into V-shaped units on either side of the body
    • each muscle unit receives a branch from the main nerve cord; lack any appendages
    • similar system found in all living vertebrates
section 29 2 invertebrate chordates53
Section 29-2Invertebrate Chordates
  • How Do Invertebrate Chordates Fit Into the World?
    • By studying the invertebrate chordates, it is like using a time machine to study the ancestors of our own subphylum