1. Animal Systems II Chapter 28
How do the body systems of animals allow them to collect info about their environments and respond appropriately?

2. How do animals respond to events around them?
Most animals have a special nervous system to respond to events around them
Nervous systems are composed of specialized nerve cells called neurons
Information in the environment that causes an organism to react is called a stimulus

3. Nervous System
The nervous system has two primary functions that are critical in maintaining life of the organism:
1. Sensory receptors allow organism to monitor its external environment and detect changes (ex increase in temperature)
This allows for activation of muscles and glands to respond to these environmental changes
2. Monitors organisms internal environment
Controlling heart rate and measuring nutrient levels

4. Neuron A neuron consists of several parts: Soma- cell body
Dendrites- brings information to cell body
Axon-takes information away from cell body
Myelin sheath

6. Detecting Stimuli
Animals ability to detect stimuli depends on specialized cells called sensory neurons
Each type of sensory neuron responds to a particular stimulus such as light, heat or chemicals

7. Detecting Stimuli
Humans share many types of sensory cells with other animals. Many animals have types of sensory cells that humans lack.
This is one reason why some animals respond to stimuli that humans cannot detect; such as weak electric currents or Earth’s magnetic field

8. Analgesia
It is the loss of sensation of pain that results from an interruption in the nervous system pathway between a sense organ and brain.
Different forms of sensation (touch, temperature and pain) can stimulate an area of skin travel to the spinal cord by different nerve fibres in the same nerve bundle. Therefore, any injury or disease affecting the nerve would abolish all forms of sensation in the area supplied by it
When sensory nerves reach the spinal cord, however, their fibres separate and follow different courses to the brain

9. Processing Information
When sensory neurons detect a stimulus, they pass info about it to other nerve cells called interneurons
Interneurons process information and determine how an animal responds to stimuli
The number of interneurons an animal has and the ways they process information determines how flexible and complex an animal can be
Ex: some invertebrates such as cnidarians and worms have very few interneurons and are capable of only simple responses to stimuli

10. Responding
When an animal responds to a stimulus, body systems (sensory neurons, nervous system and muscles) work together to generate a response
Nerve cells called motor neurons carry “directions” from interneurons to muscles

11. Motor Neurons in Vertebrates
There are three different forms of motor neurons in vertebrates depending on species
Muscles of the limbs which are involved in locomotion
Another involves brachial muscles (motorize the gills in fish)
Movement of cardiac and smooth muscles (muscles of the arteries)

12. Nervous System Evolution
Animal nervous systems exhibit different degrees of cephalization and specialization
Cephalization is the process through evolution of the sensory and neural organs to be concentrated in a anterior head

13. Invertebrates
Invertebrate nervous systems range from simple collections of nerve cells to complex organizations that include many interneurons
Cnidarians, such as jellyfishes, have simple nervous systems called nerve nets
Nerve nets consist of neurons connected into a netlike arrangement with few specializations

15. Invertebrates
In symmetric invertebrates, such as sea stars, some interneurons are grouped together into nerves, or nerve cords, that form a ring around the animals’ mouths and stretch out along their arms
In other invertebrates, a number of interneurons are grouped together into small structures called ganglia, in which interneurons connect with one another

16. Organization of Interneurons
Interneurons form ganglia in several places, with the largest ganglia typically located in the head region and called cerebral ganglia
In some species, cerebral ganglia are further organized into a structure called a brain
The brains of some cephalopods, such as octopi, enable complex behavior, including several kinds of learning

17. Parts of the Vertebrate brain
Regions of the vertebrate brain include the cerebrum, cerebellum, medulla oblongata, optic lobes, and olfactory bulbs

18. Parts of the Vertebrate Brain
The cerebrum is the “thinking” region of the brain. It is also involved in learning, memory and conscious thought
It receives and interprets sensory information and determines a response
The cerebellum coordinates movement and controls balance
The medulla oblongata controls the functioning of many internal organs
Optic Lobes are involved in vision and olfactory bulbs are involved in the sense of smell

19. Brain Evolution
Brain evolution, in vertebrates follows a general trend of increasing size and complexity from fishes, through amphibians and reptiles, to birds and mammals
In fishes, amphibians, and reptiles, the cerebrum, or “thinking” region, is relatively small
In birds and mammals, and especially in primates, the cerebrum is much larger and may contain folds that increase its surface area
The cerebellum is also most highly developed in birds and mammals

20. Brain of rainbow trout

21. Sensory Systems
Sensory systems vary in complexity including both sensory neurons and other cells that help gather information
Many invertebrates have sense organs that detect light, sound, vibrations, movement, body orientation, and chemicals in air or water
Flatworms, for example have simple eyespots that detect only the presence and direction of light

22. Chordate Sense Organs
Although all mammalian ears have the same basic parts, they differ in their ability to detect sound
Bats and dolphins can find objects in their environment using echoes of their own high-frequency sounds

23. Movement and Support
An animal’s ability to move efficiently is greatly enhanced by rigid body parts
Animals have three main kinds of skeletal systems: hydrostatic skeletons, exoskeletons, and endoskeletons

24. Hydrostatic Skeletons
Found in many cold-blooded organisms and soft bodied animals with a fluid filled cavity
The fluids held in a gastrovascular cavity can alter the animal’s body shape drastically by working with contractile cells in its body wall

25. Exoskeletons
Many arthropods and most mollusks (snails and clams) have exoskeletons
The exoskeleton of an arthropod is a hard body covering made of a protein called chitin
Most mollusks have exoskeletons made of calcium carbonate

26. Exoskeleton Functions
The various functions of an exoskeleton include:
Jointed exoskeletons enable various arthropods to swim, fly, burrow, walk, crawl, and leap
Provide watertight coverings that enable some arthropods to live in Earth’s driest places
Can provide physical protection against predators

27. Exoskeleton Disadvantages
An external skeleton poses a problem when the animal needs to grow
How is this fixed?
To increase in size, arthropods break out of their exoskeleton and grow a new one, in a process called molting
Exoskeletons are heavy

28. Endoskeleton An endoskeleton is a structural support within the body
Echinoderms and vertebrates have endoskeletons
Vertebrates endoskeleton is made of cartilage or a combo of cartilage and bone

29. Joints
Arthropods and vertebrates can bend because many parts of their skeletons are connected by joints
Joints are places where parts of a skeleton are held together in ways that enable them to move with respect to one another

30. Ligaments
In vertebrates, bones are connected at joints by strong connective tissues called ligaments
Most joints are formed by a combination of ligaments, cartilage, and lubricating joint fluid that enables bones to move without painful friction

31. Tendons
Muscles are attached to bones around the joints by tough connective tissue called tendons
Tendons are attached in such a way that they pull on bones when muscles contract

32. Muscles and Movement
In many animals, muscles work together in pairs or groups that are attached to different parts of a supporting skeleton
Muscles are specialized tissues that produce physical force by contracting, or getting shorter, when they are stimulated
Muscles can relax when they aren’t being stimulated, but they cannot actively get longer

33. Movement
In both arthropods and vertebrates, different pairs or groups of muscles pull across the joint in different directions
When one muscle group contracts, it bends, or flexes, the joint
When the first group relaxes and the second group contracts, the joint straightens
The shapes and relative positions of bones, muscles, and joints are linked very closely to the functions they perform
Differently shaped bones and muscles form limbs adapted for long-distance jumping (frogs), manipulating objects (raccoons), climbing trees (sloths), and flying (birds)

34. Reproduction
How do asexual and sexual reproduction in animals compare?
Asexual reproduction requires only one parent, so individuals in favorable environmental conditions can reproduce rapidly. Since offspring produced asexually carry only a single parent’s DNA, they have less genetic diversity than do offspring produced sexually
Sexual reproduction maintains genetic diversity in a population by creating individuals with new combinations of genes

35. Asexual Reproduction Animals reproduce asexually many ways:
Some cnidarians divide into two
Some animals reproduce via budding, which produces new individuals as outgrowths of the body wall
The process parthenogenesis, produces offspring that carry DNA inherited only from their mothers

36. Sexual Reproduction
Sexual reproduction involves meiosis, the process that produces haploid reproductive cells, or gametes
Genetic diversity is the basis on which natural selection operates, sexually reproducing populations are better able to evolve and adapt to changing environmental conditions
However, sexual reproduction requires two individuals of different sexes, so the density of a population must be high enough to allow mates to find each other

37. Sexual Reproduction
Among annelids, mollusks, and fishes, however, some species are hermaphrodites, which means that some individuals can be both male and female or can convert from one sex to the other
An example of this are clownfish, which may change from one sex to another as they mature

38. Internal & External Fertilization
How do internal and external fertilization differ?
During internal fertilization, eggs are fertilized inside the body of the egg-producing individual
Includes many aquatic and all terrestrial animals
In external fertilization, eggs are fertilized outside the body of the egg-producing individual
Includes range of aquatic invertebrates and vertebrate species

39. Embryos
Oviparous species are those in which embryos develop in eggs outside the parents’ bodies
Includes: most invertebrates, many fishes and amphibians, most reptiles, all birds, and a few odd mammals

40. Ovoviviparous Species
In ovoviviparous species, embryos develop within the mother’s body, but they depend entirely on the yolk sac of their eggs. The young do not receive any additional nutrients from the mother
The young either hatch within the mother’s body or are released immediately before hatching. They swim freely shortly after hatching.
Includes guppies and some shark species

41. Viviparous Species
Viviparous species are those in which embryos obtain nutrients from the mother’s body during development
Occurs in most mammals, sharks, amphibians and reptiles
In viviparous insects and in some sharks and amphibians, young are nourished by secretions produced in the mother’s reproductive tract
In placental mammals, young are nourished by a placenta a specialized organ that enables exchange of respiratory gases, nutrients, and wastes between the mother and her developing young

42. Metamorphosis
Metamorphosis is a developmental process that leads to dramatic changes in shape and form
In aquatic invertebrates they have a larval stage, which looks nothing like an adult
Terrestrial invertebrates go through incomplete metamorphosis. They have immature forms called nymphs that resemble adults but lack functional sexual organs and some adult structures (wings)
Amphibians metamorphosis is controlled by hormones

43. Homeostasis
Homeostasis or control of internal conditions, is essential to an organism’s survival
For example, brain cells must be bathed in fluid with a constant concentration of water and be cleansed of metabolic waste products. Failure of this, for even a few minutes could lead to brain injury or death

44. Interrelationship of Body Systems
The digestive, respiratory, circulatory, excretory, nervous, muscular, and skeletal systems are all interconnected and work together to maintain homeostasis
In most animals, respiratory and digestive systems would be useless without circulatory systems to distribute oxygen and nutrients
The excretory system needs a circulatory system to collect carbon dioxide and nitrogenous wastes from body tissues and deliver them to the lungs and excretory organs
Muscles wouldn’t work without a nervous system to direct them and a skeletal system to support them

45. Homeostasis Examples Fighting Disease Chemical Controls
Immune system to distinguish foreign pathogens from own cells
Chemical Controls
Endocrine glands regulate body activities by releasing hormones into the blood, where they are carried to the designated organs
Body temperature control
Requires three components: a source of heat, a way to conserve heat when necessary, and a method of eliminating excess heat when necessary

46. Ectotherm
Ectotherms are animals that regulate body temperature primarily by absorbing heat from, or losing heat to, their environment
They have relatively low metabolic rates when resting, so their bodies don’t generate much heat
Their muscles generate heat when active, but since most ectotherms lack effective body insulation, their body heat is easily lost to the environment

47. Endotherm
An endotherm is an animal whose body temperature is regulated, at least in part, using heat generated by its body
Have high metabolic rates that generate heat, even when they are resting
Conserve heat through feathers, body fat, hair
Remove excess heat through panting or sweating