Biology 2024-2025 Notes

MODULE 13: ANIMALS-INVERTEBRATES PART 1

Characteristics of animals- What is an animal? What characteristics are used to classify animals?

Diversity of invertebrates- What are some of the main phyla of invertebrates? What characteristics do members of each phyla have? Where do they live? What and how do the eat?

• Characteristics Of Animals

  all animals share four basic characteristics that separate them from organisms of other kingdoms.

• • Invertebrates and vertebrates

    Invertebrates- Animals that lack backbones.

    Vertebrates- Animas that possess a backbone.

    95% of all animal species are invertebrates. Invertebrates make up all of the phyla in the kingdom Animalia except for phylum Chordata. The other 5% of animal species are vertebrates. They include fish, amphibians, reptiles, birds, and mammals.

  • Symmetry

    Another way scientists describe animals is by their symmetry.

    Spherical symmetry- An organism possesses spherical symmetry if it can be cut into two identical halves by any cut that runs rough the organism’s center.

    Radial symmetry- An organism possesses radial symmetry if it can be cut into two identical halves by any longitudinal cut through its center.

    Bilateral symmetry- An organism possesses bilateral symmetry if it can only cut into two identical halves by a single longitudinal cut along its center that divides it into right and left halves.

    The concentration of sense organs and nerves in the head of an animal is called cephalization.

    Anterior end- the end of an animal that contains its head.

    Posterior end- the end of an animal that contains its tail.

• Diversity Of Invertebrates

  There are over 30 phylum’s of invertebrates.

  • Sponges- phylum Poriferia

    Sponges are asymmetrical.

    • Sponge anatomy

      Epidermis- An outer layer of cells designed to provide protection.

      Endodermis- An inner layer of cells.

      Mesenchyme- The jellylike substance that separates the epidermis from the inner cells of the sponge.

      A sponge is supported by a network of spicules that are found mostly in the mesenchyme. Some sponges do not have spicules. These sponges are supported by a tough web of protein called spongin.

    • Feeding

      Collar cells- Flagellated cells that push water though a sponge.

      Amoebocytes- Cells that move using pseudopods and perform different functions in different animals.

    • Reproduction

      Sponges have several modes of reproduction: sexually by budding; regeneration; gemmule.

      Gemmule- A cluster of cells encased in a hard, spicule-reinforced shell.

    • Uses of sponges

      Sponges are used for many things other than cleaning.

  • Phylum Cnidaria

    Members of this phylum have two basic forms: the polyp and the Medusa.

    Polyp- The sessile, tubular form of a cnidarian with a mouth and tentacles at one end and a basal disk at the other.

    Medusa- A free-swimming cnidarian with a bell-shape body and tentacles.

    • Cnidarian anatomy

      Cnidarian have an outer layer of cells and an inner layer of cells separated by a jellylike layer. Each of these layers of cells is an epithelium, ad they are separated by a mesoglea.

      Epithelium- Animal tissue consisting of one or more layers of cells that have only one free surface, because the other surface adheres to a membrane or other surface.

      Mesoglea- The jellylike substance that separates the epithelium cells in a cnidarian.

      The epithelial layers of cells in a cnidarian are home to nerve cells and contractile cells. The nerve cells sense outside stimuli and coordinate the organism’s response to it, while the contractile cells bend the organism’s body to produce movement. All members of phylum cnidaria have radial symmetry. Their bodies consist of tentacles, a mouth, and a sac-like gut. The tentacles catch prey by releasing nemotocysts.

      Nemotocysts- Small capsules that contain toxin that is injected into prey or predators.