Structure and Function Animal Systems II Structure and Function

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

Homeostasis Interrelationship of Body Systems Fighting Disease Chemical Controls

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

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