Download presentation
1
Arthropods and Echinoderms
Biology I: Chapter 28
2
ARTHROPODS
4
Arthropods Phylum Arthropoda Insects, crabs, centipedes, spiders
Segmented body Tough exoskeleton made of chitin Jointed appendages
5
Evolution of Arthropods
Fewer body segments Highly specialized appendages for feeding, movement and other functions
6
Form and Function in Arthropods
Complex organ systems; some only found only in this phylum Tracheal tubes (respiration) Open circulatory system Excrete wastes through saclike tubules
7
Feeding Herbivores, carnivores, omnivores, bloodsuckers, filter feeders, detritivores, and parasites Mouthparts have evolved to allow them to eat anything imaginable Pincers or fangs to sickle- shaped jaws that can cut through the tissues of captured prey
8
Respiration: Terrestrial Arthropods
Tracheal tube: one of many branching, air- filled tubes that extend throughout the body Spiracle: small opening located along the side of the body through which air enters and leaves the body Book lung: organ that has layers of respiratory tissue stacked like the pages of a book: used to exchange gases
9
Respiration: Aquatic Arthropods
Respire through feather-like gills (i.e. lobster and crabs) The horseshoe crab respires through organs: book gills
10
Circulation Open circulatory system
Well-developed heart pumps blood through arteries that branch and enter the tissues Blood leaves the blood vessels and moves through sinuses, or cavities The blood recollects in a large sinus surrounding the heart It reenters the heart and is again pumped throughout the body
11
Excretion Terrestrial Arthropods
Malpighian tubules: sac-like organ that extracts wastes from the blood and adds them to feces that move through the gut Aquatic Arthropods Diffusion moves cellular wastes from the arthropod’s body into the surrounding water
12
Response Well-developed nervous system Brain
Sophisticated sense organs, (i.e. eyes and taste receptors)
13
Movement Well-developed groups of muscles that are coordinated and controlled by the nervous system Allows arthropods to beat their wings against the air to fly, push their legs against the ground to walk, or beat their flippers against the water to swim
14
Reproduction Terrestrial Arthropods Internal fertilization
Sperm or sperm packet Aquatic Arthropods Internal or external fertilization
15
Growth and Development in Arthropods
Molting As the time for molting approaches, skin glands digest the inner part of the exoskeleton and other glands secrete a new skeleton The animal pulls itself out of the remains of the original skeleton…this can take several hours The new exoskeleton is soft and the animal is vulnerable to predators
16
Groups of Arthropods Classified based on the number and structure of their body segments and appendages-particularly their mouthparts Crustaceans Spiders and their relatives Insects and their relatives
17
Crustaceans 2 pairs of branched antennae 2-3 body sections
Mandibles: chewing mouthparts Primarily aquatic Examples: Crabs, shrimps, lobsters, crayfishes, and barnacles Range in size from small terrestrial pill bugs to spider crabs that have masses around 20 kg
18
Crustaceans Cephalothorax: region of a crustacean formed by the fusion of the head with the thorax Thorax: body part of crustacean that lies just behind the head and houses most of the internal organs Abdomen: posterior part of an arthropod’s body
19
Crustaceans Carapace: the part of the exoskeleton that covers the cephalothorax Mandible: mouthpart adapted for biting and grinding food Cheliped: one of the first pair of legs of decapods (five pairs of legs: crayfishes, lobsters and crabs) Swimmerets: flipper-like appendages used by decapods for swimming
20
Spiders and Their Relatives
Chelicerates Mouthparts: chelicerae 2 body sections 4 pairs of walking legs Horseshoe crabs, spiders, ticks, and scorpions
21
Horseshoe Crabs The oldest living arthropods
First appeared more than mya and have changed little since that time Not true crabs at all! Anatomy is closer to that of spiders Chelicerae, five pairs of walking legs, a long spike- like tail used for movement
22
Arachnids: Spiders The largest group of arachnids
Spin webs of a strong, flexible protein called silk Do not have jaws for chewing: must liquefy food to swallow it
23
Arachnids: Spiders Chelicerae: pair of mouthparts in chelicerates that contain fangs and are used to stab and paralyze prey Pedipalps: pair of mouthparts in chelicerates that are usually modified to grab prey Spinneret: organ in spiders that contains silk glands
24
Arachnids: Mites and Ticks
Small arachnids that are usually parasitic Chelicerae and pedipalps are specialized for digging into a host’s tissues and sucking out blood or plant fluids Mouthparts are so strong that if you try to pull off a tick the cephalothorax may separate from the abdomen and remain in your skin
25
Arachnids: Scorpions Widespread in warm areas around the world
Have pedipalps that are enlarged into claws The long, segmented abdomen of a scorpion carries a venomous stinger that can kill or paralyze prey Chew their prey using their chelicerae
26
Insects and Their Relatives
Uniramians have jaws, one pair of antennae, and unbranched appendages A group that contains more species than any other group of animals living today Wide variety of forms and lifestyles Centipedes Millipedes
28
Insects Have a body divided into three parts:
Head Thorax Abdomen Three pairs of legs are attached to the thorax Like all arthropods, insects have a segmented body, exoskeleton, and jointed appendages
29
Responses to Stimuli Multiple of sense organs are used to respond to stimuli Compound eyes Chemical receptors for taste and smell on their mouthparts Well-developed ears that hear sounds far above the human range
30
Adaptations for Feeding
Three pairs of appendages that are used as mouthparts, including a pair of mandibles Adaptations for feeding are not restricted to their mouthparts Many produce saliva containing digestive enzymes that help break down food
31
Movement and Flight 3 pairs of legs
Used for walking, jumping, flying, capturing and holding prey, etc. The evolution of flight has allowed insects to disperse long distances and to colonize a wide variety of habitats
32
Metamorphosis Incomplete metamorphosis: type of insect development characterized by a similar appearance throughout all stages of the life cycle Nymph: immature form that lacks functional sex organs and other adult structures
33
Metamorphosis Complete metamorphosis: type of insect development in which the larvae look and act nothing like their parents and also feed in completely different ways Pupa: stage of metamorphosis in which an insect changes from a larva into an adult
34
Insects and Humans Many insects are known for their negative effects
Termites destroy wood structures, moths eat their way through wool clothing, etc. Despite their association with destruction and disease, insects contribute to agriculture by pollinating 1/3 of the food that you eat Produce commercially valuable silk, wax and honey
35
Insect Communication Communicate using sound, visual, chemical, and other types of signals Much of the communication involves finding a mate Pheromones: specific chemical messengers that affect the behavior of development of other individuals of the same species
36
Insect Societies Ants, bees, termites, and some of their relatives form complex associations called societies Society: a group of closely related animals of the same species that work together for the benefit of the whole group Caste: group of individual insects specialized to perform particular tasks, or roles
37
ECHINODERMS
39
Echinoderms Phylum Echinodermata Live only in the sea Spiny skin
Water vascular system Tube feet: suction-cuplike structures Endoskeleton: internal skeleton; hardened plates of calcium carbonate Five-part radial symmetry
40
Form and Function in Echinoderms
The water vascular system, which is filled with fluid, carries out many essential body functions in echinoderms including respiration, circulation, and movement Madreporite: sieve-like structure through which the water vascular system of an echinoderm opens to the outside
41
Feeding Several methods of feeding
Sea urchins use five-part jaw-like structures to scrape algae from rocks Sea lilies use tube feet to capture floating plankton Sea stars feed on mollusks by pushing the stomach out through the mouth
42
Respiration and Circulation
Other than the water vascular system, echinoderms have few adaptations to carry out respiration or circulation In most species, the thin-walled tissue of the tube feet provides the main surface for respiration
43
Excretion Solid wastes are released as feces through the anus
Nitrogen-containing cellular wastes are excreted primarily in the form of ammonia It is passed through the tube feet and skin gills
44
Response Do not have a highly developed nervous system
Most have a nerve ring that surrounds the mouth and radial nerves that connect the ring with the body sections Most have scattered sensory cells that detect light, gravity, and chemicals released by potential prey
45
Movement Most move by tube feet and thin layers of muscle fibers attached to their endoskeleton Mobility is determined by the kind of endoskeleton
46
Reproduction Reproduce by external fertilization
The sexes are separate in most sea star species
47
Groups of Echinoderms 7000 species Sea urchins and sand dollars
Brittle stars Sea cucumbers Sea stars Sea lilies and feather stars
48
Ecology of Echinoderms
Common in a variety of marine habitats A rise or fall of echinoderms can cause major changes to populations of other marine organisms Sea urchins control the distribution of algae and other forms of marine life Sea stars are important carnivores that control the numbers of other organisms such as clams and corals
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.