Animal Systems IIAnimal Systems IIChapter 28Chapter 28

How do the body systems of animals How do the body systems of animals allow them to collect info about their allow them to collect info about their

environments and respond environments and respond appropriately?appropriately?

How do animals respond to How do animals respond to events around them?events around them?

►Most animals have a special nervous Most animals have a special nervous system to respond to events around system to respond to events around themthem

►Nervous systems are composed of Nervous systems are composed of specialized nerve cells called specialized nerve cells called neuronsneurons

► Information in the environment that Information in the environment that causes an organism to react is called a causes an organism to react is called a stimulusstimulus

Nervous SystemNervous System

► The nervous system has two primary functions The nervous system has two primary functions that are critical in maintaining life of the that are critical in maintaining life of the organism:organism:

► 1. Sensory receptors allow organism to 1. Sensory receptors allow organism to monitor its external environment and detect monitor its external environment and detect changes (ex increase in temperature)changes (ex increase in temperature) This allows for activation of muscles and glands to This allows for activation of muscles and glands to

respond to these environmental changesrespond to these environmental changes

► 2. Monitors organisms internal environment2. Monitors organisms internal environment Controlling heart rate and measuring nutrient Controlling heart rate and measuring nutrient

levelslevels

NeuronNeuron

► A neuron consists of several parts:A neuron consists of several parts: SomaSoma- cell body- cell body DendritesDendrites- brings information to cell body- brings information to cell body AxonAxon-takes information away from cell body-takes information away from cell body Myelin sheathMyelin sheath

Detecting StimuliDetecting Stimuli

► Animals ability to Animals ability to detect stimuli detect stimuli depends on depends on specialized cells specialized cells called called sensory sensory neuronsneurons

► Each type of sensory Each type of sensory neuron responds to a neuron responds to a particular stimulus particular stimulus such as light, heat or such as light, heat or chemicalschemicals

Detecting StimuliDetecting Stimuli

► Humans share many types of sensory cells Humans share many types of sensory cells with other animals. Many animals have with other animals. Many animals have types of sensory cells that humans lack. types of sensory cells that humans lack.

► This is one reason why some animals This is one reason why some animals respond to stimuli that humans cannot respond to stimuli that humans cannot detect; such as weak electric currents or detect; such as weak electric currents or Earth’s magnetic fieldEarth’s magnetic field

AnalgesiaAnalgesia

► It is the loss of sensation of pain that results It is the loss of sensation of pain that results from an interruption in the nervous system from an interruption in the nervous system pathway between a sense organ and brain.pathway between a sense organ and brain.

► Different forms of sensation (touch, Different forms of sensation (touch, temperature and pain) can stimulate an area temperature and pain) can stimulate an area of skin travel to the spinal cord by different of skin travel to the spinal cord by different nerve fibres in the same nerve bundle. nerve fibres in the same nerve bundle. Therefore, any injury or disease affecting the Therefore, any injury or disease affecting the nerve would abolish all forms of sensation in nerve would abolish all forms of sensation in the area supplied by itthe area supplied by it

► When sensory nerves reach the spinal cord, When sensory nerves reach the spinal cord, however, their fibres separate and follow however, their fibres separate and follow different courses to the braindifferent courses to the brain

Processing Information Processing Information

► When sensory neurons detect a stimulus, they When sensory neurons detect a stimulus, they pass info about it to other nerve cells called pass info about it to other nerve cells called interneuronsinterneurons

► Interneurons process information and Interneurons process information and determine how an animal responds to stimulidetermine how an animal responds to stimuli

► The number of interneurons an animal has and The number of interneurons an animal has and the ways they process information determines the ways they process information determines how flexible and complex an animal can behow flexible and complex an animal can be

► Ex: some invertebrates such as cnidarians and Ex: some invertebrates such as cnidarians and worms have very few interneurons and are worms have very few interneurons and are capable of only simple responses to stimulicapable of only simple responses to stimuli

Responding Responding ► When an animal responds to a stimulus, When an animal responds to a stimulus,

body systems (sensory neurons, nervous body systems (sensory neurons, nervous system and muscles) work together to system and muscles) work together to generate a responsegenerate a response

► Nerve cells called Nerve cells called motor neuronsmotor neurons carry carry “directions” from interneurons to muscles“directions” from interneurons to muscles

Motor Neurons in VertebratesMotor Neurons in Vertebrates

►There are three different forms of There are three different forms of motor neurons in vertebrates motor neurons in vertebrates depending on speciesdepending on species

►Muscles of the limbs which are Muscles of the limbs which are involved in locomotioninvolved in locomotion

►Another involves brachial muscles Another involves brachial muscles (motorize the gills in fish)(motorize the gills in fish)

►Movement of cardiac and smooth Movement of cardiac and smooth muscles (muscles of the arteries)muscles (muscles of the arteries)

Nervous System EvolutionNervous System Evolution

► Animal nervous systems exhibit different Animal nervous systems exhibit different degrees of cephalization and specializationdegrees of cephalization and specialization

► CephalizationCephalization is the process through is the process through evolution of the sensory and neural organs evolution of the sensory and neural organs to be concentrated in a anterior headto be concentrated in a anterior head

InvertebratesInvertebrates

► Invertebrate nervous systems range Invertebrate nervous systems range from simple collections of nerve cells to from simple collections of nerve cells to complex organizations that include complex organizations that include many interneuronsmany interneurons

►Cnidarians, such as jellyfishes, have Cnidarians, such as jellyfishes, have simple nervous systems called simple nervous systems called nerve nerve netsnets

►Nerve netsNerve nets consist of neurons consist of neurons connected into a netlike arrangement connected into a netlike arrangement with few specializationswith few specializations

Invertebrates Invertebrates

► In symmetric invertebrates, such as sea In symmetric invertebrates, such as sea stars, some interneurons are grouped stars, some interneurons are grouped together into together into nerves, or nerve cordsnerves, or nerve cords, that , that form a ring around the animals’ mouths form a ring around the animals’ mouths and stretch out along their armsand stretch out along their arms

► In other invertebrates, a number of In other invertebrates, a number of interneurons are grouped together into interneurons are grouped together into small structures called small structures called gangliaganglia,, in which in which interneurons connect with one anotherinterneurons connect with one another

Organization of InterneuronsOrganization of Interneurons

► Interneurons form ganglia in several places, Interneurons form ganglia in several places, with the largest ganglia typically located in with the largest ganglia typically located in the head region and called the head region and called cerebral gangliacerebral ganglia

► In some species, cerebral ganglia are In some species, cerebral ganglia are further organized into a structure called a further organized into a structure called a brainbrain

►The brains of some cephalopods, such as The brains of some cephalopods, such as octopi, enable complex behavior, including octopi, enable complex behavior, including several kinds of learningseveral kinds of learning

Parts of the Vertebrate brainParts of the Vertebrate brain

► Regions ofRegions of the vertebrate brain include the the vertebrate brain include the cerebrum, cerebellum, medulla oblongata, optic cerebrum, cerebellum, medulla oblongata, optic lobes, and olfactory bulbslobes, and olfactory bulbs

Parts of the Vertebrate BrainParts of the Vertebrate Brain► The The cerebrumcerebrum is the “thinking” region of the is the “thinking” region of the

brain. It is also involved in learning, memory and brain. It is also involved in learning, memory and conscious thoughtconscious thought It receives and interprets sensory information and It receives and interprets sensory information and

determines a response determines a response ► The The cerebellumcerebellum coordinates movement and coordinates movement and

controls balancecontrols balance► The The medulla oblongatamedulla oblongata controls the functioning of controls the functioning of

many internal organsmany internal organs► Optic LobesOptic Lobes are involved in vision and are involved in vision and olfactory olfactory

bulbsbulbs are involved in the sense of smell are involved in the sense of smell

Brain EvolutionBrain Evolution

► Brain evolution,Brain evolution, in vertebrates follows a general in vertebrates follows a general trend of increasing size and complexity from trend of increasing size and complexity from fishes, through amphibians and reptiles, to birds fishes, through amphibians and reptiles, to birds and mammalsand mammals

► In fishes, amphibians, and reptiles, the cerebrum, In fishes, amphibians, and reptiles, the cerebrum, or “thinking” region, is relatively smallor “thinking” region, is relatively small

► In birds and mammals, and especially in primates, In birds and mammals, and especially in primates, the cerebrum is much larger and may contain folds the cerebrum is much larger and may contain folds that increase its surface areathat increase its surface area

► The cerebellum is also most highly developed in The cerebellum is also most highly developed in birds and mammals birds and mammals

Brain of rainbow trout

Sensory SystemsSensory Systems► SensorySensory systems vary in complexity including systems vary in complexity including

both sensory neurons and other cells that help both sensory neurons and other cells that help gather informationgather information

► Many invertebrates have sense organs that detect Many invertebrates have sense organs that detect light, sound, vibrations, movement, body light, sound, vibrations, movement, body orientation, and chemicals in air or waterorientation, and chemicals in air or water Flatworms, for example have simple eyespots that Flatworms, for example have simple eyespots that

detect only the presence and direction of lightdetect only the presence and direction of light

Chordate Sense OrgansChordate Sense Organs

► Although all Although all mammalian mammalian ears ears have the same basic have the same basic parts, they differ in their parts, they differ in their ability to detect soundability to detect sound

► Bats and dolphins can Bats and dolphins can find objects in their find objects in their environment using environment using echoes of their own echoes of their own high-frequency soundshigh-frequency sounds

Movement and SupportMovement and Support

►An animal’s ability to move efficiently is An animal’s ability to move efficiently is greatly enhanced by rigid body parts greatly enhanced by rigid body parts

►Animals have three main kinds of skeletal Animals have three main kinds of skeletal systems: hydrostatic skeletons, systems: hydrostatic skeletons, exoskeletons, and endoskeletonsexoskeletons, and endoskeletons

Hydrostatic SkeletonsHydrostatic Skeletons► Found in many cold-Found in many cold-

blooded organisms blooded organisms and soft bodied and soft bodied animals with a fluid animals with a fluid filled cavityfilled cavity

► The The fluids held in a fluids held in a gastrovascular cavity can gastrovascular cavity can alter the animal’s body alter the animal’s body shape drastically by shape drastically by working with contractile working with contractile cells in its body wallcells in its body wall

ExoskeletonsExoskeletons►Many arthropods and most mollusks Many arthropods and most mollusks

(snails and clams) have (snails and clams) have exoskeletonsexoskeletons►The exoskeleton of an arthropod is a The exoskeleton of an arthropod is a

hard body covering made of a protein hard body covering made of a protein called called chitinchitin

►Most mollusks have exoskeletons Most mollusks have exoskeletons made of calcium carbonatemade of calcium carbonate

Exoskeleton Functions Exoskeleton Functions ► The various functions of an exoskeleton The various functions of an exoskeleton

include:include:► Jointed exoskeletons Jointed exoskeletons enable various enable various

arthropods to swim, fly, burrow, walk, crawl, arthropods to swim, fly, burrow, walk, crawl, and leapand leap

► Provide watertight coverings that enable some Provide watertight coverings that enable some arthropods to live in Earth’s driest placesarthropods to live in Earth’s driest places

► Can provide physical protection against Can provide physical protection against predatorspredators

Exoskeleton DisadvantagesExoskeleton Disadvantages

►An external skeleton An external skeleton poses a problem poses a problem when the animal needs to growwhen the animal needs to grow

►How is this fixed?How is this fixed?►To increase in size, arthropods break out of To increase in size, arthropods break out of

their exoskeleton and grow a new one, in a their exoskeleton and grow a new one, in a process called process called moltingmolting

►Exoskeletons are heavyExoskeletons are heavy

EndoskeletonEndoskeleton► An An endoskeletonendoskeleton is a structural support is a structural support

within the bodywithin the body► Echinoderms and vertebrates have Echinoderms and vertebrates have

endoskeletonsendoskeletons► Vertebrates endoskeleton is made of Vertebrates endoskeleton is made of

cartilage or a combo of cartilage and bonecartilage or a combo of cartilage and bone

JointsJoints► Arthropods Arthropods and vertebrates can bend because and vertebrates can bend because

many parts of their skeletons are connected by many parts of their skeletons are connected by jointsjoints

► Joints are places where parts of a skeleton are Joints are places where parts of a skeleton are held together in ways that enable them to move held together in ways that enable them to move with respect to one anotherwith respect to one another

Ligaments Ligaments

► In In vertebrates, bones vertebrates, bones are connected at joints are connected at joints by strong connective by strong connective tissues called tissues called ligamentsligaments

► Most joints are formed Most joints are formed by a combination of by a combination of ligaments, cartilage, ligaments, cartilage, and lubricating joint fluid and lubricating joint fluid that enables bones to that enables bones to move without painful move without painful friction friction

Tendons Tendons

► Muscles Muscles are attached are attached to bones around the to bones around the joints by tough joints by tough connective tissue connective tissue called called tendonstendons

► Tendons are attached Tendons are attached in such a way that they in such a way that they pull on bones when pull on bones when muscles contractmuscles contract

Muscles and MovementMuscles and Movement► In many In many animals, muscles work together in animals, muscles work together in

pairs or groups that are attached to different pairs or groups that are attached to different parts of a supporting skeletonparts of a supporting skeleton

►Muscles are specialized tissues that Muscles are specialized tissues that produce physical force by contracting, or produce physical force by contracting, or getting shorter, when they are stimulatedgetting shorter, when they are stimulated

►Muscles can relax when they aren’t being Muscles can relax when they aren’t being stimulated, but they cannot actively get stimulated, but they cannot actively get longerlonger

MovementMovement► In both In both arthropods and vertebrates, different pairs or arthropods and vertebrates, different pairs or

groups of muscles pull across the joint in different groups of muscles pull across the joint in different directionsdirections

► When one muscle group contracts, it bends, or flexes, the When one muscle group contracts, it bends, or flexes, the jointjoint

► When the first group relaxes and the second group When the first group relaxes and the second group contracts, the joint straightenscontracts, the joint straightens

► The shapes and relative positions of bones, muscles, and The shapes and relative positions of bones, muscles, and joints are linked very closely to the functions they performjoints are linked very closely to the functions they perform

► Differently shaped bones and muscles form limbs adapted Differently shaped bones and muscles form limbs adapted for long-distance jumping (frogs), manipulating objects for long-distance jumping (frogs), manipulating objects (raccoons), climbing trees (sloths), and flying (birds)(raccoons), climbing trees (sloths), and flying (birds)

ReproductionReproduction► How do asexual and sexual reproduction in How do asexual and sexual reproduction in

animals compare?animals compare?► Asexual reproduction Asexual reproduction requires only one parent, requires only one parent,

so individuals in favorable environmental so individuals in favorable environmental conditions can reproduce rapidly.conditions can reproduce rapidly. SSince offspring ince offspring produced asexually carry only a single parent’s produced asexually carry only a single parent’s DNA, they have less genetic diversity than do DNA, they have less genetic diversity than do offspring produced sexuallyoffspring produced sexually

► Sexual reproduction Sexual reproduction maintains genetic diversity in maintains genetic diversity in a population by creating individuals with new a population by creating individuals with new combinations of genescombinations of genes

Asexual ReproductionAsexual Reproduction

►Animals reproduce asexually many Animals reproduce asexually many ways:ways:

►Some cnidarians divide into twoSome cnidarians divide into two►Some animals reproduce via Some animals reproduce via buddingbudding, ,

which produces new which produces new individuals as individuals as outgrowths of the body walloutgrowths of the body wall

►The process The process parthenogenesisparthenogenesis, , produces produces offspring that carry DNA inherited only from offspring that carry DNA inherited only from their motherstheir mothers

Sexual ReproductionSexual Reproduction

► Sexual Sexual reproduction involves meiosis, the reproduction involves meiosis, the process that produces haploid reproductive cells, process that produces haploid reproductive cells, or gametesor gametes

► GeneticGenetic diversity is the diversity is the basis basis on which natural on which natural selection operates, sexually reproducing selection operates, sexually reproducing populations are better able to evolve and adapt to populations are better able to evolve and adapt to changing environmental conditionschanging environmental conditions

► However, However, sexual reproduction requires two sexual reproduction requires two individuals of different sexes, so the density of a individuals of different sexes, so the density of a population must be high enough to allow mates to population must be high enough to allow mates to find each otherfind each other

Sexual ReproductionSexual Reproduction

► Among annelids, mollusks, and fishes, however, Among annelids, mollusks, and fishes, however, some species are hermaphrodites, which means some species are hermaphrodites, which means that some individuals can be both male and that some individuals can be both male and female or can convert from one sex to the otherfemale or can convert from one sex to the other An example of this are clownfish, which may An example of this are clownfish, which may

change from one sex to another as they maturechange from one sex to another as they mature

Internal & External Internal & External FertilizationFertilization

► How do internal and external fertilization How do internal and external fertilization differ?differ?

► DuringDuring internal fertilizationinternal fertilization, eggs are fertilized , eggs are fertilized inside the body of the egg-producing individualinside the body of the egg-producing individual Includes many aquatic and all terrestrial animals Includes many aquatic and all terrestrial animals

► In In external fertilization, eggs are fertilized outside external fertilization, eggs are fertilized outside the body of the egg-producing individualthe body of the egg-producing individual Includes range of aquatic invertebrates and Includes range of aquatic invertebrates and

vertebrate speciesvertebrate species

Embryos Embryos

► Oviparous speciesOviparous species are those in which are those in which embryos develop in embryos develop in eggs outside the eggs outside the parents’ bodiesparents’ bodies

► Includes: mIncludes: most ost invertebrates, many invertebrates, many fishes and amphibians, fishes and amphibians, most reptiles, all birds, most reptiles, all birds, and a few odd and a few odd mammalsmammals

Ovoviviparous SpeciesOvoviviparous Species► In In ovoviviparous speciesovoviviparous species, embryos , embryos

develop within the mother’s body, develop within the mother’s body, but they depend entirely on the but they depend entirely on the yolk sac of their eggs. The young yolk sac of their eggs. The young do not receive any additional do not receive any additional nutrients from the mothernutrients from the mother

► The The young either hatch within the young either hatch within the mother’s body or are released mother’s body or are released immediately before hatching. They immediately before hatching. They swim freely shortly after hatching.swim freely shortly after hatching. Includes guppies and some shark Includes guppies and some shark

spspeciesecies

Viviparous SpeciesViviparous Species

► Viviparous Viviparous species are those in which embryos obtain species are those in which embryos obtain nutrients from the mother’s body during developmentnutrients from the mother’s body during development Occurs in most mammals, sharks, amphibians and reptilesOccurs in most mammals, sharks, amphibians and reptiles

► InIn viviparous insects and in some sharks and amphibians, viviparous insects and in some sharks and amphibians, young are nourished by secretions produced in the young are nourished by secretions produced in the mother’s reproductive tractmother’s reproductive tract

► In In placental mammals, young are nourished by a placental mammals, young are nourished by a placentaplacenta a specialized organ that enables exchange of respiratory a specialized organ that enables exchange of respiratory gases, nutrients, and wastes between the mother and her gases, nutrients, and wastes between the mother and her developing youngdeveloping young

Metamorphosis Metamorphosis

► MetamorphosisMetamorphosis is a developmental process that is a developmental process that leads to dramatic changes in shape and formleads to dramatic changes in shape and form

► In aquatic In aquatic invertebrates invertebrates they havethey have a larval stage, a larval stage, which looks nothing like an adultwhich looks nothing like an adult

► Terrestrial invertebrates go through incomplete Terrestrial invertebrates go through incomplete metamorphosis. They have immature forms called metamorphosis. They have immature forms called nymphsnymphs that resemble adults but lack functional that resemble adults but lack functional sexual organs and some adult structures (wings)sexual organs and some adult structures (wings)

► Amphibians metamorphosis is controlled by Amphibians metamorphosis is controlled by hormones hormones

Homeostasis Homeostasis

►Homeostasis Homeostasis or control of internal or control of internal conditions, is essential to an organism’s conditions, is essential to an organism’s survivalsurvival

►For example, For example, brain cells must be bathed in brain cells must be bathed in fluid with a constant concentration of water fluid with a constant concentration of water and be cleansed of metabolic waste and be cleansed of metabolic waste productsproducts. Failure of this, for even a few . Failure of this, for even a few minutes could lead to brain injury or deathminutes could lead to brain injury or death

Interrelationship of Body Interrelationship of Body SystemsSystems

► TheThe digestive, respiratory, circulatory, excretory, nervous, digestive, respiratory, circulatory, excretory, nervous, muscular, and skeletal systems are all interconnected and muscular, and skeletal systems are all interconnected and work together to maintain homeostasiswork together to maintain homeostasis

► In most animals, respiratory and digestive systems would In most animals, respiratory and digestive systems would be useless without circulatory systems to distribute oxygen be useless without circulatory systems to distribute oxygen and nutrientsand nutrients

► TheThe excretory system needs a circulatory system to collect excretory system needs a circulatory system to collect carbon dioxide and nitrogenous wastes from body tissues carbon dioxide and nitrogenous wastes from body tissues and deliver them to the lungs and excretory organsand deliver them to the lungs and excretory organs

► Muscles wouldn’t work without a nervous system to direct Muscles wouldn’t work without a nervous system to direct them and a skeletal system to support them them and a skeletal system to support them

Homeostasis ExamplesHomeostasis Examples

► Fighting DiseaseFighting Disease Immune system to distinguish foreign pathogens Immune system to distinguish foreign pathogens

from own cellsfrom own cells► Chemical Controls Chemical Controls

Endocrine glandsEndocrine glands regulate body activities by releasing regulate body activities by releasing hormones into the blood, where they are carried to the hormones into the blood, where they are carried to the designated organsdesignated organs

► Body temperature controlBody temperature control Requires three components: a source of heat, a way to Requires three components: a source of heat, a way to

conserve heat when necessary, and a method of conserve heat when necessary, and a method of eliminating excess heat when necessary eliminating excess heat when necessary

EctothermEctotherm

► EctothermsEctotherms areare animals animals that regulate body that regulate body temperature primarily by temperature primarily by absorbing heat from, or absorbing heat from, or losing heat to, their losing heat to, their environmentenvironment

► They haveThey have relatively low relatively low metabolic rates when metabolic rates when resting, so their bodies don’t resting, so their bodies don’t generate much heatgenerate much heat

► Their musclesTheir muscles generate heat generate heat when active, but since most when active, but since most ectotherms lack effective ectotherms lack effective body insulation, their body body insulation, their body heat is easily lost to the heat is easily lost to the environment environment

EndothermEndotherm► AnAn endothermendotherm is an is an

animal whose body animal whose body temperature is regulated, temperature is regulated, at least in part, using heat at least in part, using heat generated by its bodygenerated by its body

► Have high metabolic rates Have high metabolic rates that generate heat, even that generate heat, even when they are restingwhen they are resting

► Conserve heat through Conserve heat through feathers, body fat, hairfeathers, body fat, hair

► Remove excess heat Remove excess heat through panting or through panting or sweatingsweating