CHARACTERISTICS OF ANIMALS Characteristics of Animals What characteristics

CHARACTERISTICS OF ANIMALS

Characteristics of Animals • What characteristics do all animals share? • Animals, which are members of the kingdom ANIMALIA, are: • Multicellular • Heterotrophic • Eukaryotic

Characteristics of Animals – Animals are all heterotrophs; they obtain nutrients and energy by eating other organisms. – Animals are also multicellular; their bodies are composed of many cells. – The cells that make up animal bodies are eukaryotic, containing a nucleus and membrane-bound organelles.

Types of Animals • All animals can be divided into two types: - Invertebrates - Vertebrates (Chordates)

Invertebrates • Invertebrates include all animals that lack a backbone, or vertebral column.

Invertebrates • More than 95 percent of animal species are informally called invertebrates. Invertebrates include at least 33 phyla. • • Invertebrates include: sea stars, worms, jellyfishes, and insects. They range in size from dust mites to giant squid more than 20 meters long.

Vertebrates • All chordates exhibit four characteristics during at least one stage of life: • • a dorsal, hollow nerve cord a notochord a tail that extends beyond the anus pharyngeal pouches.

Vertebrates • Fewer than 5 percent of animal species are chordates.

Needs for Survival

What Animals Do to Survive • Animals must reproduce • Animals must maintain homeostasis by: • responding to information • obtaining and distributing oxygen and nutrients • collecting and eliminating carbon dioxide and other wastes

Maintaining Homeostasis • Often, homeostasis is maintained by feedback inhibition, or negative feedback, a system in which the product or result of a process limits the process itself. • for example, if you get too cold, you shiver, using muscle activity to generate heat • or if you get too hot, you sweat, which helps you lose heat

Responding to Information • The nervous system gathers information using cells called receptors that respond to sound, light, chemicals, and other stimuli.

Responding to Information • Some invertebrates have only a loose network of nerve cells, with no real center. • Other invertebrates and most chordates have large numbers of nerve cells concentrated into a brain. A leech has 32 brains! But not the brains you think of…

Obtaining and Distributing Oxygen and Nutrients • All animals must “breathe” to obtain oxygen. • organ systems • diffusion

Obtaining and Distributing Oxygen and Nutrients • All animals must “eat” to obtain nutrients. • Most animals have a digestive system that acquires food and breaks it down into forms cells can use.

Obtaining and Distributing Oxygen and Nutrients • After acquiring oxygen and nutrients, animals must transport them to cells throughout their bodies by using some kind of circulatory system.

Obtaining and Distributing Oxygen and Nutrients • Open Circulatory System – pump blood into a hemocoel with the blood diffusing back to the circulatory system between cells • Hemocoel - cavity or series of spaces between the organs of most arthropods and mollusks through which the blood circulates • Closed Circulatory System – blood is pumped by a heart through vessels, and does not normally fill body cavities.

Collecting and Eliminating CO 2 and Other Wastes • Animals’ metabolic processes generate carbon dioxide and other waste products, some of which contain nitrogen in the form of ammonia. • Both carbon dioxide and ammonia are toxic in high concentrations and must be excreted, or eliminated from the body.

Reproducing • Most animals reproduce sexually by producing haploid gametes. Reproduction of Various Animals VIDEO

Reproducing • Many invertebrates and a few vertebrates can also reproduce asexually (1 parent). • Asexual reproduction produces offspring that are genetically identical to the parent.

Reproducing • Sexual reproduction (2 parents) helps create and maintain genetic diversity, which increases a species’ ability to evolve and adapt as its environment changes.

Reproducing Terms to know: • Viviparous - Bringing forth live young that have developed inside the body of the parent • Oviparous - Producing young by means of eggs that are hatched after they have been laid by the parent • Ovoviparous - Producing young by means of eggs that are hatched within the body of the parent

ANIMAL BODY PLANS and EVOLUTION

Features of Body Plans • Features of animal body plans include: • • levels of organization body symmetry differentiation of germ layers formation of body cavities patterns of embryological development segmentation cephalization limb formation

Levels of Organization • As the first cells of most animals develop, they differentiate into specialized cells that are organized into tissues. A tissue is a group of cells that perform a similar function.

Levels of Organization • Tissues combine during growth and development to form organs and organ systems that carry out complex functions.

Body Symmetry • The bodies of most animals exhibit some type of symmetry. • Radial • Bilateral • Asymmetrical

Differentiation of Germ Layers • During embryological development, the cells of most animal embryos differentiate into three layers called germ layers. • Endoderm • Mesoderm • Ectoderm

Differentiation of Germ Layers • Cells of the endoderm, or innermost germ layer, develop into the linings of the digestive tract and much of the respiratory system. • Cells of the mesoderm, or middle layer, give rise to muscles and much of the circulatory, reproductive, and excretory organ systems. • The ectoderm, or outermost layer, produces sense organs, nerves, and the outer layer of the skin.

Formation of a Body Cavity • Most animals have some kind of body cavity—a fluidfilled space between the digestive tract and body wall. • A body cavity provides a space in which internal organs can be suspended and room for those organs to grow.

Formation of a Body Cavity • Most complex animal phyla have a true coelom, a body cavity that develops within the mesoderm and is completely lined with tissue derived from mesoderm.

Formation of a Body Cavity • Some invertebrates have only a primitive jellylike layer between the ectoderm and endoderm. • Other invertebrates lack a body cavity altogether, and are called acoelomates.

Formation of a Body Cavity • Still other invertebrate groups have a pseudocoelom, which is only partially lined with mesoderm.

Patterns of Embryological Development • Every animal that reproduces sexually begins life as a zygote, or fertilized egg. • As the zygote begins to develop, it forms a blastula, a hollow ball of cells.

Patterns of Embryological Development • As the blastula develops, it folds in on itself, forming an elongated structure with a tube that runs from one end to the other. This tube becomes the digestive tract.

Patterns of Embryological Development • At first this digestive tract has only a single opening. However, an efficient digestive tract needs two openings.

Patterns of Embryological Development • In phyla that are protostomes, the blastopore becomes the mouth. The anus forms from a second opening. • Most invertebrates are protostomes.

Patterns of Embryological Development • In deuterostomes, the blastopore becomes the anus, and the mouth is formed from a second opening that develops. • Chordates and echinoderms are deuterostomes.

Segmentation: Repeating Parts • As many bilaterally symmetrical animals develop, their bodies become divided into numerous repeated parts, or segments.

Cephalization: Getting a Head • Animals with bilateral symmetry typically exhibit cephalization, the concentration of sense organs and nerve cells at their anterior end. • The most successful animal groups, including arthropods and vertebrates, exhibit cephalization.

Limb Formation: Legs, Flippers, and Wings • Segmented, bilaterally symmetrical animals typically have external appendages on both sides of the body.

Limb Formation: Legs, Flippers, and Wings • These appendages vary from simple groups of bristles in some worms, to jointed legs in spiders, wings in dragonflies, and a wide range of limbs, including bird wings, dolphin flippers, and frog legs.

Body Plans • The body plans of modern invertebrates and chordates suggest evolution from a common ancestor.