Chapter 8 Critical Thinking

1. Hagfishes and lampreys are the only living representatives of a very ancient group. Why do you suppose there are still some of these jawless fishes around?

For one thing, nature revolves around the fat that those organisms that are more successful than others will live longer. As for both hagfishes and lampreys, they are the most well adapted species of the class Agnatha, since they are still living today. It’s simply when you place natural selection into play – only the best survive. Hagfishes and lampreys may have not been the “top” predator when before, but in the overall outcome, they are the most successful ones since they are “living fossils.”

2. A deep-water shark, new to science, is collected for the first time. The specimen is studied in detail, but its stomach is empty. How could you get a rough idea of its feeding habits? The specimen is a female, and its reproductive tract is found to contain 20 eggs. Can you tell the type of development characteristics of this species?

· A factor which makes this question very broad is the fact that there is little to no information for this scenario. And although hypothesis may be assumed, giving that it has been studied in detail and has an empty stomach, one can derive the answer to be that the shark is a filter feeder, or in such cases that it has a slow metabolic rate because of its lifestyle, which therefore means that the food that has been consumed prior to its capture has moved from the shark’s stomach and into it’s intestine.

· Out of the three types of shark egg development – viviparous, oviparous, and ovoviviparous, as well as the factor that it has not been observed in a contained or wild environment, there would be no way of proving the type of developmental characteristics of the newly found species yet.

3. Individuals of some species of bony fishes change sex, some to maintain more males than females, others more females than males. What are the advantages and disadvantages of each situation? Are there any advantages and disadvantages in having an equal number of males and females?
• The advantage for maintaining more males than females is that it would ensure that the most dominant male(s) would be able to mate to pass on their traits making their offspring genetically advantageous in comparison to other offsprings whose parents may have not been the dominant of the group; however, due to the amount of females, there would be less offspring.
• An advantage that more females than males offers is that that certain species would produce more offspring; but, because of that, the survival rate of the offspring would be low.
• As for the equal amount of males and females, for one, there would be a higher amount of offspring > to the scenario where there would be more males then females; yet, there would be an average survival rate, as for the factors dealing with genetics, well; it would quite hard to determine this factor since juvenile fishes are exposed to a vast amount of danger when they are maturing.

DISSECTION: SEA STAR (STARFISH)

Pictures found in: Sea star

Digestive System: The digestive system of a sea star is quite complex, with its mouth on its underside and anus on the top. They feed by everting, part of their stomach inside out through the mouth to envelop the food. The stomach then secretes digestive enzymes produced by large digestive glands that extend into the arms. The digested food is carried into the glands for absorption and the stomach pulled back inside the body.

Circulatory System: Sea stars do not have a circulatory system.

Nervous System: Sea stars have a network of nerves that coordinates movements of tube feet and spines in the absence of a brain.

Excretory System: There is no formal excretory system present in sea stars.

Reproductive System: Sea stars reproduce by means of broadcast spawning where the males and females discharge there eggs and sperm into the water where they are fertilized.

Integumentary System: The integumentary system of a sea star consists of five arms and spines or bumps all over its body. The spines are protective and also help with respiration.

Body Plan: Unlike many organisms, the sea star and the rest of its echinoderm family have a pentamerous radial symmetry and also lack a head. They have no anterior or posterior end or even a dorsal or ventral side. It is useful to refer to one of its surfaces as oral, because that is where the mouth is located, and an opposite side - referred to as aboral. They also have an endoskeleton similar to humans, that is secreted within the tissues, rather than externally.

Sea stars live in temperate and tropical waters. Some are bottom dwellers while many live mostly in shallow marine environments. They eat scraps of food, algal mats, or even deceased organisms. Others are active predators that will attack and eat clams, snails, sponges, corals, anemones.

DISSECTION: CLAMS

Pictures found in: Clams

Digestive System: Water is drawn into siphons formed by the fusion of the edge of the mantle which leads to its mouth then to its digestive glands and then to its intestines.

Circulatory System: Water is siphoned into its mantle which passes over its gills, where oxygen is then diffused into the blood and pumped through its body via impulses of the heart. CO2 is then diffused out as O2 takes its place within the gills.

Nervous System: A clam has no formal nervous system, but it senses its environment with the use of its ganglia that is located above the mouth and foot, cells along the edge of its mantle react to both light and touch.

Reproductive System: Each clam has a gonad - with each being either a male or female. They reproduces sexually through means of broadcast spawning where both egg cells and sperm cells are released into the water, where they get fertilized.

Integumentary System: Enclosed in a CaCO3 shell that is adapted to protect its soft body from predators. Its foot is used for locomotion.

Body Plan: Its soft interior is protected by a hard shell composed of CaCO3. It's body is covered by a mantle: a thin layer of tissue that secretes the shell. It is unsegmented and bilaterally symmetrical and has a ventral muscular foot that is used for locomotion.

Different species of clams live in different environments - ranging from fresh to saltwater. Clams are simple organisms. Clams are molluscs because they are soft bodied animals with an internal or external shell. The name of the phylum is derived from Latin word molluscus meaning soft.

DISSECTION: SQUIDS

Pictures found in: Squid

Digestive System: The squid has a flow through digestive system. Food enters their digestive tract through the squid's mouth and is digested into feces which is excreted through the anus.

Circulatory System: The squid has a closed circulatory system with three hearts. H2O and O2 enter the squid's body through its mantle where the respiratory exchange takes place in the gills. CO2 and H2O are then expelled from the body through a siphon.

Nervous System: A squid has a very complex nervous system compared to most invertebrates. Having They have a large brain that coordinates and stores information received around its environment. Also, by using their giant nerve fibers, they can rapidly conduct impulses, which allows them to capture their prey at great velocities.

Excretory System: The excretory system of a squid if also known as a metanephridium, which consists of a ciliated funnel opening into the body cavity and to a duct which opens to its exterior. These ciliated tubes assist in the pumping out waste products.

Reproductive System: The reproduction in squids is external - where the male uses a modified arm to transfer a spermatophore to the female.

Integumentary System: The integumentary system of a squid is enclosed in the mantle, which has two swimming fins along each side. These fins are not the main source of their motility. The skin of the squid is covered in chromatophores, which allows the squid to change color to suit its environment. The underside of the squid is also found to be lighter than the topside, in order to provide camouflage from both prey and predator (countershading).
Under the body are openings to the mantle cavity, which contains the gill and openings to the excretory and reproductive systems. At the front of the mantle cavity lies the siphon, which the squid uses for locomotion through means of jet propulsion. This is done by sucking water into the mantle cavity and quickly expelling it out of the siphon in a fast, strong jet. The direction of the siphon can be changed in order to suit the direction of travel.
Inside the mantle cavity, beyond the siphon, lies the visceral mass of the squid, which is covered in a thin skin. Under this are all the major internal organs of the squid.

Body Plan: The body plan of a squid includes its head and arms, mouth, and eyes.
The head end of the squid bears 8 arms and two tentacles. These tentacles do not grow back if severed.
The mouth of the squid is equipped with a sharp horny beak mainly made of chitin and proteins, and is used to kill and tear prey into manageable pieces.
The eyes of the squid, found on either side of the head, contains a hard lens, which is used much like the lens of a camera or a telescope for focusing; rather than changing shape, like a human eye, it moves mechanically.

Squids live in the ocean - a few, most notably the giant squid and the colossal squid live out in the colder open ocean. Many of the smaller species of squid rely on color changing patterns in order to communicate with each other and to attract prey as well. Squids are considered to be one of the most successful and highly complex of all invertebrates.

DISSECTION: CRAYFISH

Pictures found in: Crayfish

Digestive System: The digestive system of a crayfish is simple compared to other vertebrates, but far more complex than other invertebrates. The tract is composed a foregut (enlarged stomach that is specialized for grinding), the midgut, and the hindgut - leads to anus and regulates salt and water as well. The digestive gland secretes digestive enzymes and aids in the absorption of the products of digestion.

Circulatory System: The circulatory system of the crayfish is centered on a muscular heart with dorsal, anterior, and posterior arteries leading away from it. The heart pumps the blood across the gills which absorbs the oxygen from the water and sends it back to the heart and adjoining arteries.

Nervous System: A crayfish's nervous system is composed of a ventral nerve cord fused with segmental ganglia, and the supresophageal and subesophageal ganglia.

Excretory System: The excretory organs are also called the antennal glands are located at the base of the second antenna. They excrete the waste products of blood filtration.

Reproductive System: Crayfishes reproduce sexually during the spring.

Integumentary System: The crayfish has a jointed exoskeleton which they shed to allow growth.

Body Plan: The body is divided into two parts: the cephalothorax and the abdomen. The cephalothorax has sensory, feeding, and locomotion functions and the abdomen has locomotion and visceral functions.

Crayfish live in freshwater environments - any where there is a rich muddy water that allow them to hide.

Homework: Invertebrates

1. Name of organism (Classification kingdom, phylum, class, order, family, genus, species)

Picture found in: NOAA: Horseshoe Crab
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Cheilcerata
Class: Merostomata
Subclass: Xiphosura
Order: Xiphosurida
Family: Limulidae
Genus: Limulus
Species: polyphemus

2. Habitat (where in the ocean does it live)
Horseshoe crabs can tolerate a wide range of temperatures and have distinct physiological processes that enable them to survive in areas of low oxygen environments. Adult horseshoe crabs have been found burrowed into muds and intertidal flats at low tide. They can move out of the water during spawning and survive extended periods of time out of the water as long as their book gills are kept moist. Since horseshoe crabs go through inshore and offshore migrations, they are particularly affected by environmental degradations in both estuarine and oceanic habitats.

3. Food source
Adult horseshoe crabs feed primarily on marine worms and shellfish, including razor clams and soft-shelled clams, and since they lack jaws, horseshoe crabs use the spiny bases of their legs to crush and grind their food and to push it into their mouths.

4. Description of life cycle (egg to death)
After fertilization, the eggs begin to develop into trilobite larvae. By day five, miniature legs are visible inside the translucent egg. On day six, the larvae molt for the first time. On day seven, the outer membrane of the egg ruptures and the inner membrane swells to replace it. By the end of the second week, the larvae will molt twice for its preparation of hatching. (The rate of which the egg hatches is determined by the tides and warmth of the sun which ranges from a two week period ~ three or four weeks or even months.) Upon hatching, their digestive system is not yet functional; instead, they swim around for about a week absorbing the yolk sac as their digestive systems mature. Around day 21, the larvae settle from the water column and onto the soft sediments; there, they shed their shells, their bodies expand, a telson grows, and chitin hardens the new carapace. Horseshoe crabs molt an average of three or four times a year, where sub-adults (horseshoe crabs that are five to seven years old) appear to molt annually, until they reach until they reach sexual maturity (males = 16 ; females = 17). Their lifespan is currently unknown, but some scientist think that they may live up to 20 years or more. As for the unlucky ones, they may get eaten during their larvae form or even by birds when they are struggling to get to their upright position.

5. How does it move (if it moves)
Horseshoe crabs move by the use of their seven pairs of leg-like appendages found under their shell, which are used for gathering and eating food as well.

6. Unique characteristics
-One of the oldest living life forms
-Resemble trilobites (during their larvae stage)
-Their blood is of value to medical science which is harvested by biomedical labs and used to test the sterility of surgical instruments before surgery

7. Role in the ecosystem
A horseshoe crab is virtually a "walking hotel," with several numbers of creatures living attached to its shell: mollusks, bryozoans, sponges, flatworms, diatoms, fungi, and bacteria. Horseshoe crabs also play a big role in terms of bird migratory patterns where recent bird count shave shown alarming decreases in numbers due to horseshoe crab over-harvesting.

Critical Thinking Questions: Mass Re-Collection

Critical Thinking

Chapter 1

1. In Chapter 1 it was explained that the statement “There are mermaids in the ocean” is not a valid scientific hypothesis. Can the same be said of the statement “There are no mermaids in the ocean”? Why?

Yes, it is not a valid hypothesis as well. Both statements – “There are mermaids in the ocean” and “There are no mermaids in the ocean” are the same, since there is no factual documentation of any mermaids so far; therefore, any justification and hypothesis stating that “there are…” and “there are no mermaids in the ocean” are and should be irrelevant.

Chapter 3

3. If you owned a seaside home and a bad storm brought heavy winds and high surf to your coastline, would you prefer it to be during a new moon or a quarter moon? Why?

Hopefully it would be during the quarter moon because the tidal influence based on gravitational calculations^* would not be as great as the tidal influence that both the moon and Sun would have during a new moon.

^*F_{G moon} = Gm₁m₂ / r²

F_{G sun}= Gm₁m₂ / r²

F_{G sun} > + F_{G moon} ≈ tidal influence during the new moon and Sun

Chapter 4

1. During the day, algae carry out both photosynthesis and cellular respiration, but at night, when there is no light, they can only perform respiration. Small, isolated tide pools on rocky shores are often inhabited by thick growths of seaweeds, which are algae. Would you expect that amount of oxygen in the water to differ between night and day? How?

Because the amount of dissolved oxygen is proportional to the temperature of the ocean, it can be deduced that there would be more oxygen dissolved at night than day. Yet, there is a factor that should be taken in consideration – the water’s heat capacity. During the day, the water remains warm while the land remains hot, in contrast, at night, the water becomes cool and the land becomes cold because they are exposed to the zero degree Kelvin space. Therefore, in conclusion, I would suggest yes – in that there would be a difference in the amount of dissolved oxygen in the water in the day <>

Chapter 5

2. An autotrophic protist, such as a diatom or a dinoflagellate, can evolve into a heterotrophic protest (and therefore a protozoan) simply by losing its chloroplasts. Under what conditions might this take place?
   

For an autotrophic protest having an evolutionary stage, it may be comparable with the evolutionary stages of insects (as an example). The protist, it goes through an evolutionary process where the organism’s biological structure goes through several changes during its juvenile stage – thus losing its autotrophic attributes and gaining heterotrophic values, which may be triggered by its maturity or even a chemical change in the water thru means of natural or artificial alteration.

Chapter 6

2. Only very few flowering plants have invaded the oceans, but those that have are very successful. What are some possible reasons for the small number of marine flowering plants? How do those that have taken the step manage to thrive in some environments?

Here are some possible reasons for the small number of marine flowering plants:

· Inadaptability to salt water

· Temperature dependent

· Competition

· Ability to withstand wave crashing zones

· Tidal range

Over a process of natural selection, the many flowering plants that thrive in these environments have developed highly productive meadows and forests along the shore.

Class Work: Division and Multiplication

1. What is DNA?
DNA - the Blueprint of Life
*Every living organism contains within itself the information it needs to build a new organism.
2. What are the 4 bases?
In DNA they are A, T, C and G; where A stands for adenine, T for thymine, C for cytosine and finally G for guanine.
3. What 2 peices of information did the scientists need to solve the elusive structure of DNA?
Phosphate backbone, double helix.
4. What are the specific base pairs?
(adenine,thynine) (guanine,cytosine)
5. How does the pairing rule effect the shape and structure of DNA?
A and T makes a 2H and G and C makes 3H bond, which restricts the structure of the DNA block during its copying process.
6. What does the DNA do during cell division?
DNA unwinds so it can be copied and the copies transferred to new cells. DNA also unwinds so that its instructions can be used to make proteins and for other biological processes.
7. How many base pairs does E. Coli have? How long does it take to replicate? How is the DNA packaged in the cell?
4, 639, 221
40 minutes
It is packaged in a tight coil in the nucleus of a cell
8. How many base pairs does Human DNA have? How long does it take to replicate? How is the DNA packaged in the cell?
3 billion + base pairs
12 – 24 hours
In the nucleus

1. What is RNA? How different is it from DNA?
RNA - a Blueprint Copy
Ribonucleic acid is a blueprint copy of DNA. RNA is only made of a single strand. Furthermore, the base T, thymine, is replaced by U, uracil in RNA.
2. How are the RNA messages formed?
RNA messages are formed by the grouping together of 3 of the letters to create a triplet or codon. The codons line up and form a chain of codes that create a message.
3. How are the RNA messages interpreted?
Ribosomes read the messages and then attach the amino acids together to make up a protein.

1. Describe cell cycle.
Gap 1 phase: cell growth begins
Synthesis phase: chromosomes duplicate and divide; cell growth continues
Gap 2 phase: cell reaches proper size
Mitosis phase: cell division
*chromosomes are stored in the cell nucleus
*CDK and cyclin are the key molecules that control and coordinate cell division
2. What is nuclear division?
Nuclear division is the division of the nucleus and genetic information into more than one cell from a parent cell, usually through mitosis or meiosis.
3. What is interphase?
When the cell or nucleus is not in mitosis.
4. Cytokinesis?
The stage in meiosis in which the cytoplasm of the cell is divided after the nuclear division.
5. Homologous chromosomes?
Pair of chromosomes that have the same genetic sequencing because they come from the same parent cell.
6. Phases of mitosis.
Prophase
Metaphase
Anaphase
Telophase
Interphase
7. Phases of meiosis and how it is different from mitosis.
Early prophase
Late prophase
Metaphase
Anaphase
Telophase
Second Telophase
*Meiosis is different from mitosis because the cell goes through 2 divisions instead of just one and results in 4 daughter cells instead of only 2.
*Cells that go through mitosis are called diploid cells because it has 2 complete sets of chromosomes. Cells that go through meiosis only have a single set of chromosomes that is completed when the female and male gamete are united.
8. Describe the process and purpose of crossing over.
Crossing over occurs only when the sperm and egg chromosomes pair up and swap genetic information, reducing the number of chromosomes to a complete set. It is important because it allows the number of chromosomes the normal number and also allows the genetic information to remain present in the cell.