1. Structure and Function
Animal Systems II
Structure and Function

2. Response Most animals have a nervous system and respond by:
Detecting Stimuli
Stimulus
Sensory neurons
Processing Information
Interneurons
Responding
Response
Motor neurons

3. Response Trends in invertebrate nervous system evolution:
Nerve Nets, Nerve Cords, and Ganglia
“Heads”
Brains

4. Response Trends in chordate nervous system evolution:
Parts of the Vertebrate Brain
Cerebrum: learning, memory, conscious thought
Cerebellum: coordinates movement, controls balance
Medulla oblongata: controls functioning of many internal organs

5. Response Vertebrate Brain Evolution Increasing in size and complexity
Fishes  amphibians and reptiles  birds and mammals

6. Sensory Systems Invertebrate Sense Organs Chordate Sense Organs
Many have sense organs that detect:
light, sound, vibrations, movement, body orientation, and chemicals in the air or water
Chordate Sense Organs
Vertebrates have highly evolved sense organs
Sensitive organs of taste, smell, and hearing

7. Movement and Support Skeletal Support
Hydrostatic Skeleton: skeleton made of fluid-filled body segments that work with muscles to allow the animal to move
Examples: cnidarians, annelids
Exoskeleton: external skeleton; tough external covering that protects and supports the body of many invertebrates
Examples: arthropods, mollusks
Endoskeleton: internal skeleton; structural support system within the body of an animal
Examples: echinoderms, vertebrates
Joint: place where one bone attaches to another bone
Ligament: tough connective tissue that holds bones together in a joint

8. Muscles and Movement Tendons Movement
Tough connective tissue that connects the skeletal muscles to bones
Movement
When one muscle group contracts, it bends or flexes the joint
When the first group relaxes, and the second group contracts, the muscle straightens
Vertebrate Muscular and Skeletal Systems
An amazing variety of complex combinations of bones, muscle groups, and joints

9. Reproduction Asexual Sexual Reproductive Cycles
Benefits: quick, no energy to find a mate
Setbacks: less genetic diversity
Sexual
Benefits: increased genetic diversity
Setbacks: slow, energy to find a mate
Reproductive Cycles
A number of invertebrates have life cycles that alternate between sexual and asexual reproduction
Some alternate between two body forms (example: cnidarian polyps and medusas)

10. Reproduction
Internal Fertilization: Eggs are fertilized inside the body of the egg-producing individual
Invertebrates
From sponges to arachnids
Some females pull sperm out of the water; in many arthropods, males deposit sperm inside the female’s body
Chordates
Some fishes and amphibians, and all reptiles, birds, and mammals
In some amphibian species, males deposit “sperm packets” into the surrounding environment and females pick them up
Most male chordates have an external sexual organ that deposits sperm inside the female

11. Reproduction
External Fertilization: eggs are fertilized outside the body of the egg-producing individual
Invertebrates
Corals, worms, mollusks
Release eggs and sperm into the water
Synchronized with tides, phases of the moon, or seasons
Fertilized eggs develop into free-swimming larvae that typically develop for a long time before changing into the adult form
Chordates
Most non-vertebrate chordates, many fishes and amphibians
Spawn in a school or in pairs

12. Development and Growth
Where Embryos Develop
Oviparous: species in which embryos develop in eggs outside a parent’s body
Most invertebrates, many fishes and amphibians, most reptiles, all birds, and a few odd mammals
Ovoviviparous: species in which the embryos develop within the mother’s body but depend entirely on the yolk sac of their eggs
Guppies and other fishes in their family, some shark species
Viviparous: animals that bear live young that are nourished directly by the mother’s body as they develop
Most mammals, some insects, sharks, bony fishes, amphibians, and reptiles

13. Development and Growth
How Young Develop
Young look like miniature adults
Metamorphosis: process of changes in shape and form of a larva into an adult; often controlled by hormones
Aquatic Invertebrates: many have a larval stage, which looks nothing like an adult
Terrestrial Invertebrates: insects may undergo one of two types of metamorphosis
Amphibians: undergo metamorphosis from aquatic young to terrestrial adults

14. Development and Growth
Complete Metamorphosis
Pupa: stage in complete metamorphosis in which the larva develops into an adult
Incomplete Metamorphosis
Nymph: immature form of an animal that resembles the adult form but lacks functional sex organs
Care of Offspring
Varies from no care to years of nurturing

15. Reproductive Diversity in Chordates
Amniotic Egg: egg composed of shell and membranes that creates a protected environment in which the embryo can develop out of water
Reptiles, birds, a few mammals
Mammalian Reproductive Strategies
Monotremes
Marsupial
Placentals

16. Homeostasis Interrelationship of Body Systems Fighting Disease
Chemical Controls

17. Homeostasis Body Temperature Control
Ectotherm: animal whose body temperature is determined by the temperature of the environment (old term: “cold blooded”)
Most reptiles, invertebrates, fishes, and amphibians
Endotherm: animal whose body temperature is regulated, at least in part, using heat generated within its body (old term: “warm blooded”)
Birds and mammals

18. Homeostasis Evolution of Temperature Control Ectotherms to endotherms
Evidence suggests some dinosaurs were endotherms
Endotherm evolved twice
reptiles  birds
reptiles  mammals