FINAL QUESTION #1

ROUNDWORM:

EVOLUTION/ NATURAL SELECTION:
The evolutionary ancestors of roundworms had a bi-directional digestive system In other words, they took in food, digested it, and distributed the nutrients through channels where they could be directly absorbed by tissues. Whatever waste was left over was expelled through the mouth. In other words, their digestive systems were just sacs. Roundworms evolved to have a unidirectional digestive system. Food is taken in through the mouth, processed in a long tube where nutrients are absorbed into tissues. The waste is excreted from the anus.

CHARACTERISTICS:

*Feeding
-Roundworms eat little growths such as fungi when they are in soil. The parasite, roundworm, will eat bodily fluids from the host. This includes blood and mucus.

*Digestion:
-digest their food by having a tubular digestive system. This means that it has openings at both ends, for ingesting food and removing wastes respectively. They do not have the stomach, therefore the food is taken directly into the intestines where enzymes are produced to aid in the absorption of nutrients.

*Reproduction:
-Roundworms are parasites that depend on an animal or plant host for their survival. A roundworm reproduces by having a female that carries an egg and a male that fertilizes it. A single roundworm is capable of laying as much as 200,000 eggs in one day.

*Respiration:
-Roundworms (nematodes) do not contain a respiratory system. Their cells give off carbon dioxide and pick up oxygen from the moist environment. If they are placed in a dry environment they will die.


*Circulation:
-A roundworm has no heart or blood vessels. 

*Nervous System:
-Four peripheral nerves run the length of the body on the dorsal, ventral, and lateral surfaces. Each nerve lies within a cord of connective tissue lying beneath the cuticles and between the muscle cells

THE DISSECTION:
*Missed the dissection; watching the dissection video instead.

EARTHWORM:

EVOLUTION/NATURAL SELECTION:
Worms began as relatively simple organisms that lived in aqueous habitats. Indeed, when the evolution of animals began some 600 million years ago, the primary habitat of all living organisms was the sea. Creatures lived in the ocean, on the surface of the ocean floor, or slightly beneath the muddy ocean floor

CHARACTERISTICS: 

*Feeding:
-Earthworms eat decaying animals and roots and plants. Some people say that worms eat the dirt it self, which is not part of there nutrition and is expelled.

*Digestion:
-An earthworm has a digestive system. It eats dirt, digesting the plant and animal matter in the dirt and then eliminates the rest. It has an esophagus for the food to go down, a crop to store the food in, a gizzard that grinds the food down, intestines for the food to pass through and take out nutrients and an anus for the food to come out. 

*Reproduction:
-earthworms must mate to reproduce, even though one earthworm contains both male and female reproductive organs. Eggs are formed in a slime tube that slips over the worm's head and forms a cocoon or capsule that incubates them. Eggs develop into tiny worms in the cocoon and crawl out through one end when ready to emerge.

*Respiration:
-Earthworms breathe through their moist skin. Gas exchange takes place directly there.

*Circulation:
-a closed circulatory system, meaning that its blood is confined to blood vessels and its blood is recirculated so it gets maximum use. An earthworm has no lungs but uses its body's surface area to absorb oxygen from the soil. The oxygen is taken in by the dorsal blood vessel and travels to the five aortic hearts by the esophogus where it is pumped to the lower, ventral blood vessel.

*Nervous System:
-The nervous system of the earthworm is "segmented" just like the rest of the body. The "brain" is la bunch of nerve tissue/sensory tissue. The brain is important for movement: if the brain of the earthworm is removed, the earthworm will move continuously. Each segment gets sensory information from only a local region of its body and controls muscles only in this local region.

THE DISSECTION:

-looked very straight forward and simple on the inside

-saw one long tube which had all the organs in/around it

-felt squishy on the inside

-saw dirt inside

GRASSHOPPER:

EVOLUTION/NATURAL SELECTION:

Grasshoppers have evolved to be quick and jump powerfully and long distance because they are preyed upon by most species. However, this has caused for predators to also evolve over time making it an endless cycle.

  
   

CHARACTERISTICS:

*Feeding:

-Grasshoppers are herbivores, which means they are plant eaters. Their food choices depend on the location: It can range from grass, trees and shrubs found in residential neighborhoods to farmers' crops. Any type of vegetation suits their appetite.

-two sets of lips/jaws/sharp and powerful teeth

*Digestion:

-Much of the digestive system of a grasshopper is similar to that of a human. Food is taken in through the mouth and expelled through the anus in the form of feces. Along the way it passes through three different guts and is broken down through a process of chewing and digestive juices.

*Reproduction:

-Grasshoppers reproduce sexually. During fertilization the male places a sperm packet into the females reproductive organ. Once the eggs are fertilized the female deposits the eggs into the ground.

-Grasshoppers reproduce after mating by having the female lay about 8-25 eggs in a layer of foam that she excretes, that forms a protective shell around the eggs. The eggs hatch and go through a process called incomplete metamorphosis where they shed their skins 5-6 times. 

*Respiration:

-help of trachea
-air filled tubes that are open at the surfaces of the thorax along with their abdomen with the help of a pair of spiracles. 
-spiracles are a kind of valves that allow oxygen to enter and carbon dioxide to escape.

*Circulation:

-Grasshoppers have open circulatory systems, with most of the body fluid filling body cavities and appendages

-the one closed organ called the dorsal vessel extends from the head through the thorax to the anus. It is a continuous tube with two regions: the heart, which is connected to the abdomen; and the aorta, which goes from the heart to the head through the thorax. 

*Nervous system:

-The grasshopper's nervous system is controlled by ganglia which are loose groups of nerve cells that are found in most species. In grasshoppers, there are ganglia in each segment as well as a larger set of sensory tissue in the head, which would be considered the brain

 THE DISSECTION:
-Very hard shell
-distinguished it to be female from the shape of the hind
-could clearly see all organs
-SMELLED TERRIBLE 

STARFISH:

EVOLUTION/NATURAL SELECTION:

The fossil record for starfish is ancient, dating back to the Ordovician around 450 million years ago, but it is rather poor, as starfish tend to disintegrate after death. Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate. 

Their reproductive organs have evolved over time that the starfish can now reproduce even though it is fragmented.

CHARACTERISTICS:

*Feeding:

- the starfish turns its stomach inside out, drops it over the prey’s body, then draws it in again when the prey is nearly digested along with its digestive juices

*Digestion:

-digest food through their stomach: the cardiac and pyloric. In the pyloric stomach digestive enzymes are secreted to help in the absorption of nutrients. A starfish's diet includes small fishes, clams, and algae.

*Reproduction:

-Starfish are able to reproduce both sexually and asexually. There are both male and female starfish and fertilization takes place externally. Some species of starfish may be able to reproduce if they become fragmented. 

*Respiration:

-Starfish breathe through two mechanisms. They have papulae that are things that dot the surface of their skin to allow oxygen from the water in and tube feet that scatter around the body surface which do the same thing

*Circulation:

-simple circulation

-The starfish has radial canals that go through all the legs and join in the center to make the water vascular system that functions as a circulatory system, waste removal and more

*Nervous system:

-The central nervous system of a starfish consists of a radial nerve running the length of each ray

-nerve ring that connects the radial nerves. 

-the nerve ring doesn't seem able to do any kind of processing of information. Instead, all the sensory information must go to the radial nerves, any memories must be stored in the radial nerves, and any decisions about what to do must be made in the radial nerves. Somehow, the five different radial nerves must coordinate those decisions if the starfish is going to get anywhere

THE DISSECTION:

-thought it would be hard, very squishy

-had white dots all over the surface

-was able to pop the stomach in and out

-the gonads were visible on the inside 

-able to isolate the stomach and look at it

THE FROG!!!

EVOLUTION/NATURAL SELECTION:

Frogs were considered water animals until they soon evolved to become amphibians, meaning they can live in water and on land. They also evolved into having teeth, making it easier to live on land and eat their prey.

CHARACTERISTICS:

*Feeding:

-Frogs start off as tadpoles, eating mostly leafy greens and algae.  Eventually they step it up and begin to eat insects and other easy prey.  By the time they reach adult status, frogs are strictly carnivores.

-use their sticky tongues to catch prey

*Digestion

-Frogs digest food using digestive enzymes in the stomach. Once that process is done, the food continues to move to the small intestine to do most of the digestion.

*Reproduction

-Frogs reproduce through external fertilization. The female frog lays the eggs in water in a slimy mass. The male frog swims over and fertilizes the eggs after they've been lain. The eggs then hatch into tadpoles that will later grow into adult frogs.

*Respiration:

-Frogs can breathe through their lungs and skin. While swimming underwater, frogs can breathe by absorbing oxygen through their skin. This process is called cutaneous gas exchange.

*Circulation:

-Frogs have three-chambered hearts

-oxygenated blood from the lungs and de-oxygenated blood from the respiring tissues enter the heart through separate atria. When these chambers contract, the two blood streams pass into a common ventricle before being pumped via a spiral valve to the appropriate vessel, the aorta for oxygenated blood and pulmonary artery for deoxygenated blood. The ventricle is divided into cavities which lowers the mixing of the two types of blood

*Nervous system

-frog has a highly developed nervous system that consists of a brain, spinal cord and nerves. Many parts of the frog's brain correspond with those of humans. It consists of two olfactory lobes, two cerebral hemispheres, a pineal body, two optic lobes, a cerebellum and a medulla oblongata. 

-size of the cerebrum in frogs is much smaller than it is in humans. Frogs have ten pairs of cranial nerves which pass information from the outside directly to the brain, and ten pairs of spinal nerves which pass information from the extremities to the brain through the spinal cord

THE DISSECTION:

-my favourite dissection
-able to look at EACH organ specifically
-extremely colourful
-had so much fat, it was clearly eating huge flies
-able to open mouth and see tongue/teeth
-able to open eyelid
-I feel like I have now completed a right of high school passage: the frog dissection.