Marsupial Reproduction
Knowledge can be obtained and conveyed in a variety of ways. One can
spend hours upon hours hidden away in the corner of a library, reading the
thoughts and discoveries of other researchers and writers. Or, one can allow
himself to make his own discoveries through experiments and observations that
he makes himself.
Both methods are necessary in order to come to a complete understanding
of a topic. An experimenter cannot fully appreciate the things that she
observes without having a background in that area. In the same way, a man does
not truly use the knowledge he has gained from book research without applying
it to the real world in some way.
Knowledge of marsupial reproduction is this way. There is much to be
learned from the writings of scientists of the past, while at the same time
there are many new discoveries to be made as researchers of the present apply
this knowledge to answering new questions. The purpose of this paper is to
compile knowledge that has already been written on marsupial reproduction,
including the topics of: marsupial characteristics, reproductive anatomy,
sexual behavior, development of young, hormonal control, and ecological
implications of reproductive patterns, so that it can be used as a basis for
new insights and discoveries.
What is a marsupial?
Many biologists of the past and present have been intrigued by a group of
animals known as marsupials. Marsupials are a subdivision of mammals with
several defining characteristics. First, marsupials generally have more
incisor teeth than eutherian (placental) mammals. In most marsupials, as in
most primates, the first toe of the hind foot is opposable to the other four,
and it always lacks a claw. Interestingly, most terrestrial marsupials have
lost this toe altogether. Marsupials also tend to have a smaller brain than
eutherians of equivalent size and their body temperature and rate of metabolism
are slightly lower than eutherians. (Gould, 52)
Other important characteristics of marsupials come from their unique
reproductive patterns and reproductive system. Externally, differences
include ìsuch interesting anatomical features as a prepenal scrotum and biparte
penes and vaginae in most groups and typically, but not always, a pouch over
the teats.î (Bronson, 187) The major difference is the dramatically
abbreviated period of gestation marsupials have adopted and the function of
this phenomenon. Few marsupials have a gestation period longer than their
oestrous cycle. This means that all marsupials give birth to highly altrical
puts their mind to a task at hand they can accomplish it most of the
Biological evolution is a change in the characteristics of living organisms over generations (Scott, 2017). A basic mechanism of evolution, the genetic drift, and mutation is natural selection. According to Darwin's theory of evolution, natural selection is a process in nature in which only the organisms best adapted to their environmental surroundings have a higher chance of surviving and transmitting their genetic characters in increasing numbers to succeeding generations while those less adapted tend to be eliminated. There has been many experimental research projects that relate to the topic of natural selection and evolution.
There is common plan for all limbs: one bone, followed by two bones, then a bunch of little bones, and finally digits. This array of bones is seen in many species including, but not restricted to bats, whales, and lizards. But how do these limbs develop and why do they all look similar? Shubin explains it by conveying that there are certain genetic switches that help assemble who we are. When scientists went looking for this genetic switch in limbs, they found a couple tissue areas in the limbs that allow this body plan to occur. “A strip of tissue at the extreme end of the limb bud is essential for all limb development…This patch of tissue was named the zone of polarizing activity (ZPA).” ZPA allows humans to have opposable thumbs and pinkies. In other organisms, it differentiates the “thumb” side from the “pinky” side. Scientists then wanted to discover the molecule that allowed this changen in the ZPA, the answer is Sonic hedgehog. Shubin points out that every limbed animal h...
They have wide chests and their arms are longer than their legs. Chimpanzees’ hands have four long fingers plus an opposable thumb. Their feet have five toes which includes an opposable big toe. Chimpanzees’ can grasp things with both their hands and their feet. Male chimpanzees are larger than female chimpanzees and are slightly sexually dimorphic. Chimpanzees are quadrupeds that typically walk using the soles of feet and the knuckles of their hands. They sometimes walk upright only when they need to use their arms to carry things but this is a rare occurrence. Chimps are also good at brachiating and climbing trees which is where they spend most of their time even when they sleep. Their dental formula is 2.1.2.3. Chimpanzees’ have y5/x4 molars, making them frugivores, and a diastema to fit their upper canines. Their diet includes fruit, leaves, flowers, seeds, smaller mammals, birds, insects, and grubs. When chimps aren’t resting, they can be very active. I enjoyed watching the Chimpanzees’ swing on the ropes and climb up and down the trees. Chimpanzees are
watching and looking at the things around him. He said that an enemy of his
which he uses to see into the minds of others. He gets into their heads and
The Harlem Renaissance, originally known as “the New Negro Movement”, was a cultural, social, and artistic movement during the 1920’s that took place in Harlem. This movement occurred after the World War I and drew in many African Americans who wanted to escape from the South to the North where they could freely express their artistic abilities. This movement was known as The Great Migration. During the 1920’s, many black writers, singers, musicians, artists, and poets gained success including Zora Neale Hurston, Langston Hughes, Marcus Garvey, and W.E.B. Du Bois. These creative black artists made an influence to society in the 1920’s and an impact on the Harlem Renaissance.
Monotreme Reproductive Biology and Behavior. Monotremes are mammals that are oviparous, or egg-laying. There are only 3 extant species of monotremes: the playtpus and two species of echidna. Their reproductive systems are highly specialized to facilitate both the production of eggs and milk.
Bipedalism is a form of locomotion that is on two feet and is the one factor that separates humans from other forms of hominoids. The first bipeds are believed to have lived in Africa between 5 and 8 million years ago. (Haviland et al. 2011, pg. 78). The evolution to bipedalism resulted in various anatomical changes. To be able to balance on two legs, the skull must be centered over the spinal column. As bipeds evolved, the foramen magnum, the opening at the base of skull for the spinal column, moved from the back of the skull to the center. The spinal column also evolved from a continuous curve to a spine with four concave and convex curves. (Haviland et al. 2011, pgs. 79, 80). Another change was the widening of the pelvis which gives a wider plateau for more balance when walking on two legs.
When was the last time you saw a sporting event and thought what you just saw was incredible? That whoever just did that was superhuman? Now put this through your mind. That athlete could improve his or her already superb skills into something even greater. This can be possible with the help of steroids. There is a current debate of allowing steroids to be legal in sports. Steroids should not be allowed in sports. Some people ask why. This research paper will give those people just a few of the many reasons why it should not be allowed. Through examining dangers of steroid abuse, ethics in sports, and characteristics of individuals who take and use steroids, it is evident that steroids should not be allowed in sports.
As the use of performance enhancing drugs is becoming more popular amongst athletes, many of them do not understand the risks involved in taking these drugs. Many people are looking for a quick way to build muscles, or to get stronger the fastest way possible. Using these performance aids may very well be a quick fix for many athletes, but taking the drugs is unethical and dangerous. Using special drugs to boost an athlete’s performance is degrading to sports and to the athlete, but after they stop using the drugs and lose some strength, you become trapped in the steroid cycle.
Anabolic steroid use is very dangerous and illegal in the USA. Steroid abuse is where danger comes into play. Anabolic steroids can be used safely with many positive effects and minimize the side effects if used safely, and in moderation. "I used steroids. It was a risky thing to do, but I have no regrets. It was what I had to do to compete. The danger with steroids is overusage. I only did it before a difficult competition – for two months, but not for a period of time that could harm me. And then afterward, it was over. I would stop. I have no health problems, no kidney damage or anything like that from using them." (Schwarzenegger) The positive side effects of steroids include increase in the male sex hormone (testosterone); which spikes improved recovery rate, increase in euphoria, gain in strength and size, increase in sex drive, and beco...
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The Harlem Renaissance was a huge transition for people of African American descent. It started in the early 1920’s and ended during the late 1920’s as well. People had moved from the southern states where Jim Crow laws were enforced, where discrimination was at its highest. Many people who were writers, entertainers and actors took this as an opportunity to grow as artists. During this time, culture was one of the only things they had left. Those who lived within Harlem needed the positivity to look up to during these hard times.
...ot see the side of whom they are inside, but they only see what they are.