Biology Notes Chapter 26

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Biology Notes Chapter 26

• Sponges, Cnidarians, and Unsegmented Worms

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Introduction into the Animal Kingdom

• An animal is a multicellular eukaryotic
  heterotroph whose cells lack cell walls.
• A heterotroph is an organism that is unable to
  make their own food so they must take food
  substances in.

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Cell Specialization Division of Labor

• The bodies of animals contain many types of
  specialized cells.
• Each specialized cell has a shape, physical
  structure, and chemical composition that make it
  uniquely suited to perform a particular function
  within a multicellular organism.
• The different specialized cells carry out
  different tasks for the organism.
• This is known as division of labor.

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What animals must do in order to
survive.

• In order to survive, animals must be able to
  perform a number of essential functions.
• Feeding animals have evolved a variety of ways
  to feed.
• Herbivores, or animals that eat plants, may feed
  on
  roots, stems, leaves, flowers or
  fruits.
• Some herbivores even feed on the nutrient rich
  fluids in plant vascular tissue.
• Carnivores, or organisms that eat animals, feed
  on any part of their prey.
• Parasites live and feed either inside or attached
  to outer surfaces of other organisms, doing harm
  to their hosts and not providing any benefit for
  the host.

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Feeding Continued

• Many aquatic organisms, called filter feeders,
  strain tiny floating plants and animals form the
  water around them.
• Many animals feed not on living organisms but on
  tiny bits of decaying plants and animals called
  detritus.
• Detritus feeders are easy to overlook but are
  important parts of the living world.

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Respiration

• Living cells consume oxygen and give off carbon
  dioxide in the process of cellular respiration.
• Therefore the entire animal must respire, or
  breathe in order to take in and give off these
  gases.
• Small animals that live in water or in moist soil
  may respire through their skin.
• Large animals skin is not an effective means of
  respiration.
• Their respiratory systems have evolved many
  different forms suited to their environment.

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Internal Transport

• Some aquatic animals, such as small worms, can
  function without an internal transport system.
• Once an animal reaches a certain size, it must
  somehow carry oxygen, nutrients, and waste
  products to and from cells deep within its body.
• Many animals have evolved circulatory system in
  which a pumping organ called a heart forces a
  fluid called blood through a series of blood
  vessels.

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Excretion

• Cellular metabolism produces chemical wastes such
  as ammonia that are harmful and must be
  eliminated.
• Small aquatic animals depend on diffusion to
  carry waste away.
• Larger animals both in water, and on land, must
  work to remove poisonous metabolic wastes.
• These animals have excretory systems that remove
  these harmful wastes from their bodies.

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Response

• Animals must keep watch on their environment.
• They must find food, spot predators, and identify
  others of their own kind.
• To do this they use specialized cells called
  nerve cells, which hook up together to form a
  nervous system.
• Sense organs, such as eyes and ears gather
  information from the environment by responding to
  light, sound, temperature, and other stimuli.
• The brain which is the nervous system control
  center, processes the information and regulates
  how the animal responds.
• The complexity of the nervous system varies
  greatly from species to species.

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Movement

• Some animals are sessile, which means they do not
  move from place to place.
• Most animals move around their environment.
• In order for movement to occur animals use
  specialized tissue called muscle tissue.
• Muscles that work with a skeletal system are the
  most effective and efficient.
• There are two kinds of skeletal systems.
• Endoskeleton, which are located within the body
• Exoskeleton, which is located outside the body
• This is why you can see a fly long after it dies.

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Reproduction

• Animals must reproduce or there species will not
  survive.
• There are two types of reproduction
• Sexual reproduction is when a male and a female
  unite to produce an offspring.
• Asexual reproduction occurs when a single parent
  supplies all the genetic information for the
  offspring.

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Reproduction Continued

• The sexual and asexual generations in animals are
  both diploid, meaning that the offspring will
  have the same number of chromosomes as the
  parents.
• Many animals that reproduce sexually bear their
  young alive while some lay eggs.
• The eggs of some of these animals hatch into
  babies that look just like miniature adults.
• As these grow these babies increase in size but
  do not change in overall form.
• This is known as direct development.

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Reproduction Continued

• In other species, eggs hatch into larvae, which
  are immature stages that look and act nothing
  like the adults.
• As larvae grow, they undergo a process called
  metamorphosis, in which they change shape
  dramatically.
• This kind of development is called indirect
  development.

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Trends in Animal Evolution

• The levels of organization become higher as
  animals become more complex in form.
• Some of the simplest animals have radial
  symmetry.
• These animals have body parts that repeat around
  an imaginary line drawn through the center of
  their body.
• Animals that exhibit radial symmetry never have
  any kind of real head.

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Trends in Animal Evolution

• Animals that have body parts such as arms and
  legs that repeat on either side of an imaginary
  line drawn down the middle of their body exhibit
  bilateral symmetry.
• Bilateral symmetry is when one side of the body
  is a mirror image of the other side.
• Animals that exhibit bilateral symmetry have
  specialized front and back ends as well as upper
  and lower sides.

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Trends in Animal Evolution

• The anterior is the front end of the animal.
• The posterior is the back end of the animal.
• The dorsal is the upper side of the animal.
• The ventral is the lower side of the animal.

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Trends in Animal Evolution

• More complex animals tend to have a concentration
  of sense organs and nerve cells in the head
  region.
• This is called cephalization.
• Nerve cells in the head gather into clusters that
  process the information gathered by the nervous
  system and control responses to stimuli.
• Small clusters of nerve cells are called ganglia,
  which are found in lower life forms such as the
  worm.
• When these clusters are quite large and complex
  we call them brains, which are found in the more
  complex organisms such as humans.

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Sponges

• Sponges are among the most ancient of all animals
  that are alive today.
• Sponges belong to the phylum Porifera.
• Sponges have nothing that resembles a mouth, or a
  gut.
• Sponges have no specialized tissue or organ
  systems. .
• It is for these reasons that sponges are thought
  to have evolved from a single celled ancestor,
  separately from other multicellular animals.

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Form and Function in Sponges

• The body of a sponge forms a wall around a
  central cavity.
• Within this wall are thousands of openings or
  pores.
• With the aid of collar cells, which are cells
  that have a flagella (or a tail) water is brought
  into the central cavity through these tiny pores.
• Water exits the sponge through a large hole
  called an osculum.

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Form and Function in Sponges

• Spicules form the skeleton of many sponges.
• Spicules are made by amebocytes from either
  calcium carbonate or silica.
• Other sponges have skeletons made up of spongin.
• These sponges are the ones that we use as bath
  sponges.

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Feeding the Sponge

• Sponges are filter feeders that sift microscopic
  particles of food from the water that passes
  through them.
• These food particles stick to the collar cells
  where they are engulfed by the collar cell by
  endocytosis.
• Endocytosis Movement of large particles of food
  or whole organisms into a cell

                                                  
                                                
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Reproduction of Sponges

• Sponges reproduce asexually as well as sexually.
• Some sponges produce gemmules, which are
  collections of amebocytes surrounded by a tough
  layer of spicules in the sexual reproductive
  phase.
• Gemmules can survive long periods of freezing
  temps and drought, which would kill adult
  sponges. When conditions are right these gemmules
  will grow into a new sponge.
• Asexually sponges reproduce by budding.
• In this process, part of a sponge falls off of
  the parent and grows into a new sponge.

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Cnidarians (nigh-dare-ian)

• All Cnidarians exhibit radial symmetry and have
  specialized cells and tissues.
• Many Cnidarians have lifecycles that include two
  different looking stages, the sessile flower like
  polyp and the motile bell shaped medusa.

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Cnidarians Continued

• Both the polyp and the medusa have a body wall
  that surrounds an internal space called the
  gastrovascular cavity.
• Within the gastrovascular cavity is where
  digestion takes place.
• Almost all cnidarians capture and eat small
  animals by using stinging cells called
  nematocysts.
• Nematocysts are located on tentacles and contain
  a poison filled sac containing a coiled spring
  loaded dart.
• When touched these nematocysts fire the dart out
  into their prey, which injects poison into them
  killing or paralyzing them so they can be eaten.

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Unsegmented Worms

• An unsegmented worm does not have their bodies
  separated into special segments.
• The Phylum Platyhelminthes consists of simple
  animals called flatworms.
• These are the simplest animals with bilateral
  symmetry.
• Most members of this phylum exhibit enough
  cephalization or development of the anterior
  end, to have what is known as a head.

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Free Living Flat Worms

• The free-living flat worms belong to the class
  Turbellaria.
• The most familiar members of this class are
  planarians, which are the cross-eyed freshwater
  worms.
• The members of the class Trematoda are parasitic
  flatworms known as flukes.
• Some flukes are external parasites that live on
  the skin, mouth, gills, or other outside parts of
  their host.

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Internal Parasites

• Most flukes like the ones that affect humans are
  internal parasites.
• These flukes infect the blood and organs of their
  hosts.
• These flukes have complicated life cycles that
  involve at least two different host animals.

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Internal Parasites

• Members of the class Cestoda are long, flat,
  parasitic worms that live very simple lives.
• These worms have ha head called a scolex, which
  contains hooks that allow it to attach itself to
  intestines where they take in food that has
  already been digested for them.

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Round Worms

• The phylum Nematoda consists of long, thin worms
  called round worms.
• These organisms are among the simplest animals to
  have a digestive system with two openings, a
  mouth and an anus.
• All round worms have a long tube shaped digestive
  tract with openings at both ends.
• This system is very efficient because food can
  enter through the mouth and travel straight
  through the digestive tract to the anus, where
  food that cannot be digested is expelled.

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Round Worms Continued

• Round worms have simple nervous systems
  consisting of several ganglia but do not have a
  true brain.
• Round worms reproduce sexually.
• Ascaris is the parasitic roundworm that lives in
  humans.

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