TA insect.notebook
1 April 05, 2016
Feb 2408:12
We are learning:
The function and location the respiratory, circulatory, excretory, reproductive and nervous systems in an insect.
The differences between insect and vertebrate internal systems.
The cross sectional diagram of an insect. (pg 66) Internal structure of an insect.
Apr 410:17
Homework.
Add a short description to each label to explain what it does.
Apr 410:43
Task 1.
Look around the room, working in pairs, gather the information on each part of the insect and in note form, include it on your diagram.
One person writes, the other person speaks.
Apr 410:33
Circulatory system of the insect.
Insects don't have veins or arteries, but they do have circulatory systems. When blood is moved without the aid of vessels, the organism has an open circulatory system.
Insect blood, properly called hemolymph, flows freely through the body cavity and makes direct contact with organs and tissues.
A single blood vessel runs along the dorsal side of the insect, from the head to the abdomen. In the abdomen, the vessel divides into chambers and functions as the insect heart (14).
Perforations in the heart wall, called ostia, allow hemolymph to enter the chambers from the body cavity. Muscle contractions push the hemolymph from one chamber to the next, moving it forward toward the thorax and head.In the thorax, the blood vessel is not chambered. Like an aorta (7), the vessel simply directs the flow of hemolymph to the head.
Insect blood is only about 10% hemocytes (blood cells); most of the hemolymph is watery plasma. The insect circulation system does not carry oxygen, so the blood does not contain red blood cells as ours does. Hemolymph is usually green or yellow in color
Apr 410:22
Nervous system of the insect
The insect nervous system consists primarily of a brain (5), located dorsally in the head, and a nerve cord (19) that runs ventrally through the thorax and abdomen.
The insect brain is a fusion of three pairs of ganglia, each supplying nerves for specific functions. The first pair, called the protocerebrum, connects to the compound eyes (4) and the ocelli (2, 3) and controls vision. The deutocerebrum innervates the antennae (1).
The third pair, the tritocerebrum, controls the labrum, and also connects the brain to the rest of the nervous system.
Below the brain, another set of fused ganglia forms the subesopagheal ganglion (31).
Nerves from this ganglion control most of the mouthparts, the salivary glands, and the neck muscles.
The central nerve cord connects the brain and subesophageal ganglion with additional ganglion in the thorax and abdomen. Three pairs of thoracic ganglia (28) innervate the legs, wings, and muscles that control locomotion.
Abdominal ganglia innervate the muscles of the abdomen, the reproductive organs, the anus, and any sensory receptors at the posterior end of the insect.
A separate but connected nervous system called the stomodaeal nervous system innervates most of the body's vital organs. Ganglia in this system control functions of the digestive and circulatory systems. Nerves from the tritocerebrum connect to a ganglia on the esophagus; additional nerves from this ganglia attach to the gut and heart.
Apr 410:33
Digestive system
The insect digestive system is a closed system, with one long enclosed tube (alimentary canal) running lengthwise through the body. The alimentary canal is a one way street – food enters the mouth and gets processed as it travels toward the anus. Each of the three sections of the alimentary canal performs a different process of digestion.
The salivary glands (30) produce saliva, which travels through salivary tubes into the mouth.
Saliva mixes with food and begins the process of breaking it down.
The first section of the alimentary canal is the foregut (27) or stomodaeum.
In the foregut, initial breakdown of large food particles occurs, mostly by saliva. The foregut includes the Buccal cavity, the esophagus, and the crop, which stores food before it passes to the midgut.
Once food leaves the crop, it passes to the midgut (13) or mesenteron. The midgut is where digestion really happens, through enzymatic action.
Microscopic projections from the midgut wall, called microvilli, increase surface area and allow for maximum absorption of nutrients.
In the hindgut (16) or proctodaeum, undigested food particles join uric acid
from Malphigian tubules to form fecal pellets. The rectum absorbs most of
the water in this waste matter, and the dry pellet is then eliminated through
the anus (17).
TA insect.notebook
2 April 05, 2016
Apr 410:30
Reproductive system of the insect
This diagram shows the female reproductive system. Female insects have two ovaries (15), each comprised of numerous functional chambers called ovarioles (seen within the ovary in the diagram). Egg production takes place in the ovarioles. Egg are then released into the oviduct. The two lateral oviducts, one for each ovary, join at the common oviduct (18). The female oviposits fertilized eggs with her ovipositor (not pictured).
Apr 410:37
Respiratory system.
Insects require oxygen just as we do, and must "exhale" carbon dioxide, a waste product of cellular respiration. Oxygen is delivered to the cells directly through respiration, and not carried by blood as in vertebrates.
Along the sides of the thorax and abdomen, a row of small openings called spiracles (8) allow the intake of oxygen from the air. Most insects have one pair of spiracles per body segment.
Small flaps or valves keep the spiracle closed until there is a need for oxygen uptake and carbon dioxide discharge. When the muscles controlling the valves relax, the valves open and the insect takes a breath.
Once entering through the spiracle, oxygen travels through the tracheal trunk (8), which divides into smaller tracheal tubes. The tubes continue to divide, creating a branching network that reaches each cell in the body. Carbon dioxide released from the cell follows the same pathway back to the spiracles and out of the body.
Most of the tracheal tubes are reinforced by taenidia, ridges that run spirally around the tubes to keep them from collapsing. In some areas, however, there are no taenidia, and the tube functions as an air sac capable of storing air.
In aquatic insects, the air sacs enable them to "hold their breath" while under water. They simply store air until they surface again. Insects in dry climates may also store air and keep their spiracles closed, to prevent water in their bodies from evaporating.
Some insects forcefully blow air from the air sacs and out the spiracles when threatened, making a noise loud enough to startle a potential predator or curious person.
Apr 410:40
Excretory system.
The Malpighian tubules (20) work with the insect hindgut to excrete nitrogenous waste products. This organ empties directly into the alimentary canal, and connects at the junction between the midgut and hindgut. The tubules themselves vary in number, from just two in some insects to over 100 in others. Like arms of an octopus, the Malpighian tubules extend throughout the insect's body.
Waste products from the hemolymph diffuse into the Malpighian tubules, and are then converted to uric acid.
The semisolidified waste empties into the hindgut, and becomes part of the fecal pellet.
The hindgut (16) also plays a role in excretion. The insect rectum retains 90% of the water present in the fecal pellet, and reabsorbs it back into the body. This function allows insects to survive and thrive in even the most arid climates.
Apr 410:15
Mrz 514:51
Tasks:
Using your knowledge, compare the following properties of insects with those of vertebrates in a table:
Eyes, Circulation (Blutkreislauf), Blood, Gas exchange (Gasaustausch), Nervous system
Insect Vertebrate
Eyes Circulation
Blood Gas exchange Nervous system
Mrz 514:51
Tasks:
Using your knowledge, compare the following properties of insects with those of vertebrates in a table:
Eyes, Circulation (Blutkreislauf), Blood, Gas exchange (Gasaustausch), Nervous system
Insect Vertebrate
Eyes Circulation
Blood does transport O2
Gas exchange Trachea
Nervous system
Compound eyes Lens eyes
open closed
does not transport O2
Lungs Head ganglia, ventral
nerve cord, decentralised
Spinal cord (dorsal) brain,
centralised.
TA insect.notebook
3 April 05, 2016
Apr 411:47
From pg 66 of the Natura 8 book, complete a diagram of a cross section of a
Apr 415:25
Apr 410:04
The Internal Anatomy of an Insect
The internal organs of insects, like those of other animals, are grouped into various systems. But these systems differ in many ways from those of other animals. The chief systems are the circulatory, respiratory, nervous, muscular, digestive, and reproductive.
Circulatory System An insect's blood does not flow through veins and arteries as ours does. Blood fills the whole cavity of the insect's body, and bathes all the organs and muscles. The blood is circulated by a long tube that lies just under the exoskeleton of the back. This tube extends almost the entire length of the body.
The pumping part of the tube lies in the abdomen, and is called the heart . The front part of the tube extends into the head, and is called the aorta . Blood enters the tube through little openings, called ostia, along the sides. The openings have valves that allow blood to enter the tube, but not to flow out. As the heart contracts, the blood is forced along the tube and out through the aorta. The blood first bathes the brain, and then flows to other parts of the body. It then reenters the tube through the ostia.
Unlike our blood, an insect's blood has little to do with bringing oxygen to the cells. Insect blood is greenish, yellowish, or colorless. Few insects have red blood.
Respiratory System An insect breathes by means of tiny holes, called spiracles , along the sides of its body. Each hole leads into a large tube called a trachea . The large tubes divide into small tubes, which, in turn, divide into still smaller tubes that branch out to all the cells of the body. This system of tubes carries oxygen to the cells and takes away carbon dioxide.
Nervous System consists of a brain, located in the head, and two nerve cords that lie side by side along the floor of the thorax and abdomen. The brain receives information from the eyes and antennae, and controls the insect's body activities as a whole. Another nerve center in the head is connected to the brain and controls the insect's mouth parts <mouth.htm>. Each of the two nerve cords contains a cluster of nerve cells, called a ganglion, in each segment of the thorax and abdomen. The two ganglia in each segment are fused and form a sort of little brain that controls the activities of that segment. The ganglia often can work without the brain. For example, many insects that have had their heads cut off can still walk, mate, and lay eggs. In some insects, the three pairs of ganglia in the thorax are fused into one. Various pairs of ganglia in the abdomen are also fused in many insects.
Muscular System is made up of several hundred to a few thousand small but very strong muscles. Grasshoppers have about 900 muscles, and caterpillars have from 2,000 to 4,000. By contrast, man has fewer than 700 muscles. Many insects can lift or pull an object 20 or more times heavier than the weight of their bodies. Few men can lift a weight heavier than the weight of their bodies.
Digestive System of an insect consists basically of a long tube that extends from the mouth to the anus. The tube has three main divisions: (1) the foregut; (2) the midgut, or stomach; (3) the hindgut, or intestine.
After food has been chewed or sucked up by the mouth parts, it enters the foregut through the mouth. The food moves along the tube until it reaches an enlarged area called the crop, where it is temporarily stored and partly digested.
Then the food passes into the gizzard, which has thick muscular walls that contract and grind the food into small bits. The gizzard of some insects has teeth that help break up and grind the food. The food next passes into the midgut, where most digestion takes place. Nourishing parts of the food are absorbed into the blood, and wastes and undigested parts move into the hindgut.
Insects have a system of 2 to over 150 malpighian tubes attached to the digestive system where the midgut and hindgut join. The tubes float in the blood and absorb waste materials, which then pass through the tubes into the hindgut.
All wastes and extra water that enter the hindgut leave the body through the anus.
Reproductive System Most insects reproduce sexually. That is, a new individual can be created only after a female sex cell (egg) has united with a male sex cell (sperm). The reproductive organs are in the abdomen. Females have two organs, called ovaries, in which eggs develop. A tube called an oviduct carries the eggs away from each ovary. The two oviducts join and form a single tube that opens near the tip of the abdomen. Male insects have two organs, called testes, that produce sperm. A tube carries the sperm from each testis. The two tubes unite and form a single tube that extends to the outside of the abdomen.
