Bellwork: How does an animal respond to it’s environment Bellwork: How does an animal respond to it’s environment? Give at least three examples of how humans respond to their surroundings

Chapter 28: Animal Systems II Response Chapter 28: Animal Systems II

How quickly does an animal respond to an event around itself? Almost instantaneously! How? Often through the use of a specialized nervous system Composed of neurons Together neurons collect information, interpret it and decide what to do with it

What is a stimulus? Anything that causes an organism to react Can be chemicals, light, heat, Ability to detect stimuli depends on sensory neurons Each sensory neuron is responds to a particular stimulus What examples can you think of? Humans share a number of sensory organs with other animals Some animals can responds to stimuli that humans can’t Eg. Electric currents or the Earth’s magnetic field

How is the information from a sensory neuron passed around the body? Interneurons – process information and determine how an organism responds to a stimuli The more complex an organisms the more interneurons The brain is essentially a mass of many interneurons

What examples of sensory responses can you think of? A response is a specific reaction to a stimulus When responding to a stimulus, often numerous body systems have to work together – often nervous and muscular system Motor neurons carry directions from interneurons to muscles

How have nervous systems evolved through time? Animal nervous systems exhibit differing degrees of cephalization and specialization Invertebrates – large amount of diversity Nerve nets, Nerve cords and Ganglia

Are heads common in invertebrates? Bilaterally symmetrical animals often exhibit cephalization Even some flatworms and roundworms display some form of cephalization Certain molluscs and arthropods show higher degrees of cephalization Ganglia form in several places, but largest in the head region (Cerebral Ganglia) Cerebral Ganglia can be further organized into a brain

What is a chordate? What are their nervous systems like? Higher degree of cephalization Highly developed nervous system Brains formed from many interneurons within the skull Human brain has more than 100 billion nerve cells! Signals sent to over 1000 nerve cells Signals received from 10,000 more

How does a brain work? A brain is divided into a series of different regions Cerebrum, Cerebellum, Medulla Oblongata, Optic lobes, and Olfactory bulbs Cerebrum: Thinking part of brain – memory, learning and conscious thought Cerebellum: Coordinates movement and controls balance Medulla Oblongata: Controls functioning of internal organs Optic Lobe: Vision Olfactory bulb: Sense of smell

Vertebrate Brains Brain evolution involves increasing size and complexity as you move to the right of a cladogram

What sense organs do invertebrates have? Many have sense organs that can detect light, sound, vibrations, movement, body orientation or chemicals in air/water Invertebrate sense organs vary widely in complexity Flatworms have tiny slits to detect presence and direction of light Some Cephalopods and arthropods have complex eyes that detect motion and color, can form images

How do vertebrates differ in their ability to hear? The hearing range of vertebrates spans from 50 Hz (tree frog) to 150,000 Hz (bottlenose dolphin) Most vertebrates have highly evolved sense organs Particularly for taste, smell and hearing Some sharks can sense 1 drop of blood in 100 liters of water Most vertebrates have color vision as good, or better than humans Some species can even (such as duckbill platypus) detect weak electrical currents in water Sharks will use ability to sense Earth’s magnetic field to navigate Similar idea to how many birds navigate Some fish generate electric current to communicate

Key point questions What does a motor neuron do? How can nervous systems vary between animal groups What is cephalization? How does it vary between animal groups? How could you tell which has a better sense of smell: Amphibians or Reptiles? What would you look for when assesing how capable an animal is of learning? What is the general relationship between the complexity of an animal’s nervous system and that of it’s sensory system