Ch 27 - Intro to Animals

27.1 Characteristics of Animals

What are the major evolutionary trends in animals? 1.Level of cellular organization and specialization 2.Body plan – symmetry 3.Degree of cephalization (head region) 4.Type of body cavity 5.Segmentation 6.Structure of digestive system

Introduction to animals

Invertebrate Groups Simplest animals; Contains the greatest number of animal species; Most found in water Do not have a backbone! Includes sponges, cnidarians, flatworms, roundworms, annelids (segmented worms), mollusks, arthropods, & echinoderms

Vertebrate Groups More complex animals; Most have a backbone Includes fish, amphibians, reptiles, birds, & mammals

TO DO: Where are these body areas? Dorsal Ventral Anterior Posterior Oral Aboral

Body Areas Dorsal is the back or upper surface Ventral is the belly or lower surface Anterior head or front end Posterior is the tail or hind end opposite the head

Oral surface in echinoderms is where the mouth is located (underside) Aboral surface in echinoderms is the surface opposite the mouth (top side)

What is symmetry? Create three organisms out of playdoh –Assymetry –Bilateral symmetry –Radial symmetry TO DO: Body Symmetry

TO DO: What animal might have the symmetry of your model? What symmetry is the most simple? »Is the most advanced?

Body Symmetry Symmetry is the arrangement of body parts around a central plane or axis Asymmetry occurs when the body can't be divided into similar sections (sponges)

Radial symmetry - body parts are arranged around a central point like spokes on a wheel Most animals with radial symmetry are sessile (attached) or sedentary (move very little)

Bilateral symmetry - animals can be divided into equal halves along a single plane (right & left sides that are mirror images) more complex, usually motile organisms, such as worms, arthropods, and all vertebrates show cephalization & have anterior & posterior ends

Mini quiz Type of symmetry? Vert or invert?

TO DO: Now show segmentation in one of your models What is true segmentation? Is the segmentation internal or external?

Segmentation Occurs whenever animal bodies are divided into repeating units or segments Found in more complex animals Earthworms show external segmentation, while humans show internal segmentation (vertebrae of the backbone) Segments may be fused together such as cephalothorax covering chest & head of a crayfish

Humans have 33 vertebrae Internal segmentation

TO DO: From zygote to induction Now form a zygote with your playdoh Next form a blastula – what does it look like? Next form a gastrula – what does it look like? –How many germ layers are there?

From zygote to induction

Zygote undergoes rapid cell divisions known as cleavage to become hollow ball of cells called blastula (except sponge) Blastocoele is the central cavity of the blastula Blastula invaginates (folds inward at one point) to form an opening & two cell or germ layers; process called gastrulation (Textbook p. 597 ) New cup-shaped structure with 2 cell layers is called the gastrula Archenteron is the deep cavity of the gastrula that forms the primitive gut Inner germ layer called endoderm & outer germ layer called ectoderm Some animals form a third germ layer in the middle called mesoderm

GastrulationGastrulation 1 min video

Opening may become the mouth or the anus Protostomes develop mouth from blastopore Deuterostomes develop an anus from blastopore

Germ layers Form the tissues, organs, & systems of an animal Found in the embryo of all animals except sponges (have specialized cells but no tissues) Ectoderm (outer) forms skin, nerves, & sense organs Endoderm (inner) forms the digestive & respiratory organs & systems Mesoderm (middle) forms muscles, circulatory system, reproductive & excretory systems

Larval Forms Some animals have indirect development & go through an immature larval form that does not resemble the adult Metamorphosis May be complete or incomplete Usually found in arthropods Incomplete metamorphosis (egg --> nymph --> adult) Complete metamorphosis ( egg --> larva --> pupa --> adult)

Body Cavities Coelom is an internal body cavity lined with mesoderm –called coelomate animals (annelids, mollusks, arthropods, & vertebrates) Acoelomate animals do not have a body cavity but have solid bodies (sponges, flatworms, & cnidarians ) Pseudocoelomate animals have a body cavity only partially lined with mesoderm (roundworms)

Support Systems Sponges are supported by spicules Hydrostatic skeletons in worms consist of a fluid-filled body cavity surrounded by muscles Arthropods have external exoskeletons that prevent water loss but must be molted for growth to occur Echinoderms & vertebrates have internal endoskeletons that grow with the organism

Digestive system All animals are heterotrophs Sponges have specialized cells to capture & digest their food Cnidarians have one opening into their gastrovascular cavity where food enters & wastes leave; called a two- way digestive system Annelids, arthropods, & vertebrates have a one-way digestive system in which food enters the mouth, is digested, & wastes leave through the anus

Circulatory system Transports oxygen and nutrients to cells & carbon dioxide and wastes away from cells Sponges, cnidarians, & flatworms don't have a circulatory system Closed systems, blood remains in blood vessels at all times until it reaches cells (earthworms & vertebrates) Open systems, blood isn't always contained in blood vessels (arthropods)

Respiratory system Oxygen is needed & carbon dioxide must be eliminated Sponges, cnidarians, flatworms, & roundworms exchange gases by diffusion Mollusks & fish use gills to exchanges gases, while terrestrial vertebrates use lungs

Nervous system Cephalization occurs in animals that have a distinct head at the anterior end where sensory organs are concentrated –found in more complex animals Sponges have specialized nerve cells, while cnidarians & flatworms have a nerve net Ganglia are clusters of nerve cells found in more complex animals Nerve cells may specialize to detect light, sound, etc. Brain interprets nerve impulses & sends a response

Body covering Integument is the outer covering of an animal Terrestrial vertebrates have water-tight outer coverings Integuments of amphibians allow gas exchange through the skin Adaptations of integuments include scales, fur, hair, & feathers to protect and insulate the body

Excretory system Rid animals of wastes, help conserve water, & filter wastes from the blood Ammonia is a toxic waste that must be gotten rid of by an animal's body Kidneys filter blood in vertebrates

Reproduction All animals reproduce sexually, some also asexual Budding - an outgrowth on the parent organism breaks off to form a new individual (ex: hydra) Fragmentation - separating into pieces & each piece making a new organism - (ex: sponges, flatworms, & cnidarians Parthenogenesis – development of unfertilized eggs (ex: insects) Hermaphrodites - produce both sperm & eggs (earthworms - cross fertilize & tapeworms self fertilize) –Each individual functions as both male and female. –Usually produced at different times so self-fertilization does not occur.

Reproduction Echinoderms, arthropods, mollusks, & vertebrates have separate sexes & exchange sperm Internal fertilization occurs inside the body of female & fewer numbers of sperm & eggs produced. –On land, egg and sperm need to remain moist. –Also serves as protection. External fertilization occurs outside the body. Most aquatic animals release male and female gametes near one another in the water. Egg is fertilized outside the female’s body. –Developing eggs may be kept inside or outside the body. –Land – may have hard shell or kept internally (most mammals) –Water – may have jelly-like shell or kept internally (some sharks)

Kinds of Animals Kingdom Animalia contains about 35 major divisions called phyla, depending on how certain organisms are classified. See the phlylogenetic tree with the evolutionary milestones. (This is a hypothesis)

Mini quiz 1.The developmental process that leads to the formation of tissue layers is A.Asexual reproduction B.Evolution C.Gastrulation D.Fertilization 2.Which of the following organisms does NOT have cells organized into tissues? A.Hydras B.Sea urchins C.Sponges D.Sea anemones C. Gastrulation C. Sponges

3. The presence of a true body cavity (coelom) allows A.Direct exchange of oxygen & carbon dioxide with the environment B.Specialization of the gut C.Cephalization D.Bilateral symmetry

4. Which of the following is NOT true of the kidneys A.They remove oxygen from the body B.They remove wastes from the bloodstream C.They produce concentrated urine D.They help balance the body’s water content A. They remove oxygen from the body