Biology Chapter 23: Invertebrates Flashcards
T/F: Animals are found nearly everywhere on Earth
True
What set of derived characteristics do all animals share, suggesting that they are all descendants of a single common ancestor?
-Multicellular heterotrophs
-Cells are supported by collagen
-Animals are diploid and usually reproduce sexually
-Most animals have Hox genes
What makes animals multicellular heterotrophs?
They must eat other organisms to survive (don’t make their own food), and they are built of many cells that help break down their food
A three-stranded protein unique to animals
Collagen
What does collagen do for animal cells?
Collagen proteins combine with each other to form strong, flexible ropelike fibers that supports cells whilst still allowing them to move within the animal’s body
What does diploid mean?
An animal has one set of chromosomes from each parent; they also reproduce offspring (usually sexually) that are also diploid
A class of genes that control early development in animals
Homeotic genes
The specific sequence of 180 nucleotides for each homeotic gene; develop the head-to-tail pattern of development in animal embryos
Homeobox, or Hox genes
How do homeotic and hox genes work?
Homeotic genes create segments in a larva or embryo that develop into specific organs and tissues
Hox genes within these segments determine the position of cell differentiation and development by switching certain genes “on” or “off”
T/F: Each animal phylum has a unique body plan
True
An animal with an internal segmented backbone
Vertebrate
Animals without backbones
Invertebrates; invertebrates, unlike vertebrates, are not defined by a set of shared derived characteristics (besides within each phylum)
A group of animals categorized by scientists, for their shared characteristics
Phylum
Each animal phylum has a unique body plan
What is the largest animal phylum amongst invertebrates?
Arthropods (86%)
What accounts for differences in animals’ body plans?
Different expressions of homeobox genes
What do scientists think led to the vast diversity of animal species?
Mutations in the Hox genes
What event, occurring approximately 500 million years ago, resulted in a dramatic increase in biological diversity in the world?
The Cambrian Explosion; an increase in oxygen levels allowed eukaryotic organisms to become more active and occupy different niches within more complex ecosystems
What 3 criteria are used to group animals?
-Body plan symmetry
-Number of tissue layers
-Developmental patterns
Body symmetry in which an animal can be divided equally along only one plane, which splits an animal into mirror-image sides
Bilateral symmetry
Body symmetry in which animals have body parts arranged in a circle around a central axis
Radial symmetry
How many tissue layers do bilateral animals have, and what are their functions?
3 (triploblastic)
Ectoderm- outer layer, develops into skin and brain and nervous system
Endoderm- inner layer that lines the animal’s gut
Mesoderm- middle layer that develops into internal tissues and organs
*Complex organ systems have resulted from the evolution of the third tissue layer
How many tissues do radial animals have, and what are their functions?
2
Inner endoderm
Outer ectoderm
*No mesoderm layer, so they therefore lack the complex internal tissues and organs that triploblastic organisms have
Describe a protostome’s developmental pattern
First opening of the digestive cavity is the mouth (anus second)
The gut cavity is formed from separations in the mesoderm
Spiral cleavage pattern
Describe a deuterostome’s developmental pattern
First opening in the digestive cavity forms the anus (mouth second)
The gut cavity forms from pouches created by the folds in the gut tube
Radial cleavage pattern
What are the defining characteristics of the Porifera phylum, and what are examples of animals in that phymum?
Sponges
-Sessile
-Filter feeders
-Asymmetrical
-2 layers of cells, called spongin, with middle, jelly-like layer
-Lack muscle and nerve cells
-Reproduce both sexually and asexually (budding)
What are the defining characteristics of the Cnidarian phylum, and what are examples of animals in that phylum?
2 Body Forms:
-Polyp, Medusa
-May reproduce sexually or asexually (budding)
-2 tissue layers separated by a non-cellular jellylike material called mesoglea
-radial body symmetry
-Sea anemones, jellyfish
Cnidarian body form: cylindrical tubes with mouth and tentacles facing upward
Polyps
Cnidarian body form: umbrella-shaped, with their mouth and tentacles on the underside
Medusas
The non-cellular jellylike material that separates the two tissue layers of cnidarians
Mesoglea
3 Types of cells in the outer tissue layer of cnidarians
Contracting cells
Nerve cells
Cnidocytes- specialized cells that contain stinging structures used for defense and capturing prey
One type of stinging structure found in cnidarians: a capsule containing a thin, coiled, harpoon-shaped tubule with a poisonous barb at one end
Nematocyst
The structure that cnidarians, such as the jellyfish, push prey into, after stinging it with their nematocysts
Gastrovascular cavity
What are the defining characteristics of the Platyhelminthes phylum, and what are examples of animals in that phylum?
Planarians (Flatworms), Flukes, Tapeworms
-Solid body that lacks a complete gut
-No circulatory system
-Parasitic (suckers) OR
-Nonparasitic (pharynx extending from mouth)
-bilateral symmetry
The infection that the parasitic flukeworm, phylum Platyhelminthes, gives to its host
Schistosomiasis
The file-like feeding organ of Mollusks
Radula
What are the defining characteristics of Mollusks, and what are examples of animals in that phylum?
Snails, Squids, Clams, Oysters, Mussels, Scallops
The area of tissue covering the internal organs of mollusks
Mantle
Flat gills found in a pocket of the mantle tissue called the mantle cavity
Ctenidia
What are the defining characteristics of the phylum Mollusca, and what are some examples of animals within that phylum?
-Snails, squids, oysters, clams, mussels
-Bilateral symmetry
-Complete digestive tract (have both mouth and anus)
-Circulatory system
Spaces between cells within a mollusk’s tissues through which some blood is pumped through
Homocoel
What are the defining characteristics of the phylum Annelida, and what are some examples of animals within that phylum?
-Earthworms
-Segmented bodies
-Closed circulatory system
-Eat organic waste material
-Can reproduce sexually or asexually (fragmentation)
-Bilateral body symmetry
What is the most defining characteristic of Annelids?
Segmented bodies
A fluid-filled space that is completely surrounded by muscle in Annelids
Coelom
What are the defining characteristics of the phylum Nematoda, and what are some examples of animals within that phylum?
-Roundworms
-Cuticle
-Bilateral symmetry
-Reproduce sexually
-Many roundworms are parasites
-No circular or respiratory system
The tough exoskeleton of Nematodes, which they must shed in order to grow
Cuticle
The fluid-filled space inside of the roundworm, separating the muscle from the central gut tube
Pseudocoelom (not a complete gut)
pseudo- “false”
What are the defining characteristics of the phylum Echinoderm, and what are some examples of animals in that phylum?
-Sea star
-Slow moving, marine animals
-Internal skeletons made up of tiny interlocking calcium-based plates (ossicles)
-Water vascular system
-Complete digestive system
-Eats by grabbing with its feet, digestive juices dissolve the prey’s body
-Can push their stomach out of their mouths
-Radial symmetry
-Reproduce sexually
The echinoderms’ internal skeleton made up of many tiny interlocking calcium-based plates
Ossicles; joined together by connective tissue with adjustable stiffness
A series of water-filled radial canals that extend along each arm from the ring canal surrounding the central disk
Water vascular system
Which 2 phyla of invertebrates are deuterostomes?
Echinoderm and Chordata
