Chapter 26 Introduction to Animals
Characteristics of Animals • There are 3 general features of animals which all animals share: • All animals are multicellular. • All animals are heterotrophs. • All animal cells lack cell walls.
Characteristics of Animals • Another feature most animals share is that they are mobile. • Certain animals, however, such as sponges and corals are immobile. http://www.hero.ac.uk/sites/hero/resources/C_Coral_vs_cricket_300.jpg http://divebarbados.net/photos/Tube%20Sponge.jpg
Two Main Classes of Animals • Animals fall into one of two categories: • Invertebrates-animals that lack a backbone. • The vast majority of animals are invertebrates. • Sponges • Ants • Squid • Vertebrates-animals with a backbone. • Cats, Dogs, Birds • Fish, Frogs, Turtles • Humans
Invertebrates • On land, these are usually very small because they do not have an internal skeleton for support. • They assist with the pollination of plants and the decomposition and recycling of dead material in an ecosystem.
Vertebrates • Vertebrates have a cranium and an internal skeleton composed of bone or cartilage. • Their vertebra protect the nerve cord and provide a site for muscle attachment.
Animal Body Systems • An animal’s skeleton provides a framework that supports the animal’s body. • There are three main types: • Hydrostatic-a water filled cavity under pressure. • Think jellyfish. http://weblogs.baltimoresun.com/news/local/bay_environment/blog/Jellyfish.jpg
Animal Body Systems • Exoskeleton-a rigid external skeleton encasing the body of the animal. • Think lobsters. http://img.dailymail.co.uk/i/pix/2007/11_01/lobsterDM0811_468x521.jpg
Animal Body Systems • Endoskeleton-a rigid internal skeleton. • Think humans. http://z.about.com/d/miniatures/1/0/1/5/-/-/skeleton.jpg
Digestive and Excretory Systems • The digestive system extracts energy and nutrients from an animal’s food. • Some animals have a gastrovascular cavity with a single opening allowing food in and out. • Other animals have a one-way digestive tract with two openings. The food moves in through the mouth, and out through the anus.
Digestive and Excretory Systems • The excretory system removes wastes from the animal’s body. • Most of these wastes are produced as a result of cellular metabolism. • Ammonia is a main waste that needs to be removed. • Animals have to remove waste products and maintain an internal osmotic balance.
Nervous Systems • The nervous system carries information about the environment through the body and coordinates a response. • There are two main types: • Simple • Complex
Simple Nervous Systems • Nerve nets have no complex arrangement. There is no coordinated response to stimuli. • Jellyfish and hydras.
Simple Nervous Systems • Other animals have clusters of nerve cells called ganglia which can coordinate responses to stimuli. • Flatworms.
Complex Nervous Systems • These animals have true brains with sensory structures. • These animals can have high level interactions with their surroundings. • Grasshoppers, humans, dolphins.
Respiratory Systems • This system is responsible for exchanging O2 and CO2 between the organisms and the environment. • Some animals have gills that allow for gas exchange in the water. • Other animals have lungs that allow for exchange on land.
Circulatory System • This system transports gases, nutrients, and other substances within the body. • Open circulatory systems-have a heart that pumps the O2/nutrient rich fluid through the body to feed the tissues and cells. • Closed circulatory systems-have a heart that pumps blood through a system of vessels.
Reproduction • Reproduction is important for the survival of a species. • There are two main strategies: • Asexual • Sexual • Each one has unique advantages and disadvantages.
Asexual Reproduction • Advantages • No need to find a mate. • Disadvantages • Little, if any, genetic diversity • One disease/illness could potentially wipe out a species.
Sexual Reproduction • Advantages • High variety within the genome. • Not as susceptible to disease. • Disadvantages • Need to find a mate.
Body Plans • Animals body plans describe the animal’s shape, symmetry, and internal organization. • The cells of all animals except sponges are arranged into units called tissues. • Tissues are groups of cells that carry out a specific function. • Tissues are often organized into organs which perform specific jobs.
Body Symmetry • Body symmetry describes how an animal’s body can be divided into similar pieces. • Asymmetry describes an animal that cannot be divided into similar pieces. • Radial symmetry describes animals whose symmetry revolves around a central axis. • Bilateral symmetry describes an animal that has right and left sides which are mirror images of each other.
Embryonic Development • The diploid zygote is the first stage of the new individual. • Cell division makes up the second stage of development. The zygote does not increase in size.
Embryonic Development • Eventually a blastula, which is a hollow ball of cells is formed.
Embryonic Development • After the blastula has formed, one side of the organism begins to pinch inward to form the gastrula. • The structure is called the blastopore.
Developmental Patterns • Eventually the blastopore reaches the other side of the organism and a second opening forms. • In protostomes, the first opening becomes the mouth. • Clams, snails, earthworms, insects • In deuterostomes, the first opening becomes the anus. • Sea stars and vertebrates
Cell Differentiation • During gastrulation, the cells of the gastrula begin increasingly different from one another.
Cell Differentiation • This leads to the formation of the three main tissue types: • Endoderm-forms the gut, respiratory system, many glands. • Mesoderm-forms most of skeleton and muscles, circulatory system, excretory organs. • Ectoderm-outer layer forms the skin, nervous system.
Body Cavities • Once the tissue layers start to form and development continues, body cavities start to form.
Body Cavities • A coelomate has a body cavity surrounded by mesoderm. • A pseudocoelomate has a body cavity, but it is not lined by mesoderm. • An acoelomate has no body cavity.
Characteristics of Chordates • At some point during development, all chordates have a dorsal nerve cord, a notochord, pharyngeal pouches, and a post anal tail.
Characteristics of Chordates • Most chordates are vertebrates. • Tunicates and lancets are invertebrate chordates and represent an evolutionary link between vertebrates and invertebrates.
The First Vertebrates • The first vertebrates evolved about 500 million years ago. • They were essentially a fish-like animal with a cartilaginous skeleton rather than a bony skeleton. • Very primitive and they lacked many of the features we think of today when we think of vertebrates--backbones and jaws.
Fish Evolution • Two features evolved in fish that set them apart from the early vertebrates: Jaws and paired fins. • These fish also had hardened spines. • The jaws allowed for grasping prey. • Fins allowed for fast swimming in pursuit of prey. • These fish were replaced by sharks and bony fishes.
Fish Are… • The most primitive vertebrates. • Share the following key characteristics: • They have endoskeletons, gills, closed-loop circulation, and kidneys. • They also have swim bladders, fins, and lateral lines. • Animals that gave rise to amphibians.
Amphibian Evolution • Early amphibians were poor swimmers and were not like frogs and toads of today. • As competition from predators increased, the numbers of species and the diversity of amphibians increased.
Amphibian Evolution • There are three characteristics that helped amphibians succeed on land: • Lungs-enabled the exchange of gases out of the water. • Heart-a more efficient way of delivering O2 to the body than a fishes heart. • Strong limbs-easy movement from place to place. • Amphibians need to keep their skin and eggs moist. They live in and around water.
Amphibians Are… • The first vertebrates to live on land. • They contain legs, lungs, double-loop circulation, a partially divided heart, and cutaneous respiration. • They are tied to the water for reproductive purposes. • Animals that gave rise to reptiles.
Evolution of Reptiles • To make the complete move to land, vertebrates needed adaptations to allow them to do so. • The watertight amniotic egg was an adaptation that allowed reptiles to move away from the water. • An amniotic egg contains yolk and a shell.
Evolution of Reptiles • The first reptiles have two important evolutionary adaptations: • Watertight, scale covered skin. • Amniotic egg. • These adaptations allow reptiles to deal with dry conditions. • The first reptiles were small dinosaurs that evolved from amphibians.
Reptiles Are… • Reptiles are animals with scales, clawed toes, and ectothermic metabolism. • Reptiles lack hair or feathers. • Dinosaurs were reptiles. • Snakes, crocodiles, turtles, turata and lizards are examples of reptiles. • Animals that gave rise to birds and mammals (from therapsids). http://eatmorecookies.files.wordpress.com/2008/08/tuatara-on-forest-floor-three-quarters.jpg
Evolution of Birds • Birds evolved from meat eating dinosaurs. • They had skeletons that were very much like dinosaurs. • The Archaeopteryx fossil (about the size of a crow) represents an intermediate form of a bird between the dinosaurs and modern birds.
Archaeopteryx • Had long teeth, arms with fingers and claws. • It lacked a breastbone to anchor flight muscles. • It had solid bones instead of hollow ones. • It had feathers on its wings and a tail, a wishbone (fused collarbone).
Birds Are… • Animals that lay amniotic eggs, have scales that cover their legs and feet, have feathers, endothermic metabolism, a beak, a lightweight skeleton, and lungs with air sacs.
Evolution of Mammals • Early mammals were about the size of mice, kept down by the dinosaurs. • After the dinosaurs and other large marine reptiles died out, mammals increased in size, took to the oceans and came to be the dominant life forms of today.
Mammals • There are three types of mammals: • Monotremes - lay eggs which quickly hatch. • Marsupials - give birth to live young that crawl into a pouch to complete their development. • Placental Mammals - give birth to live young that may or may not require extended care. • All three reproduce by internal fertilization.
Mammals Are… • Animals that evolved from mammal-like reptiles called therapsids. • Have an endothermic metabolism, mammary glands, specialized teeth, body hair.