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Population growth

Submitted by mpetracchi on Thu, 10/17/2019 - 22:12

Species on earth usually follow a similar growth pattern which scientists have been able to observe and quantify. In general, a species will experience a higher growth rate when at lower population densities until it reaches a plateau at its carrying capacity. The carrying capacity is the number of individuals an environment can sustain indefinitely. The most basic way to describe this model is through a logistic growth curve. It begins exponential and levels out. However, this is not the full story in real life. What tends to happen is a population will overshoot the carrying capacity when times are good and population growth rates are positive. When this happens the environment imply cannot sustain this population and the species feels the impact via two factors. Decreased birth rates from less food and possible increased emigration to other suitable ranges. The growth rate then decreases and the population may undershoot the carrying capacity at which point the cycle may repeat. Populations that over-and-under shoot by very little can be described as dampened oscillations.

An unfortunate problem some species face is the allee effect of population growth. The trend most observed in the wild is when population density is low for a certain area, the growth rate is high because the environment can sustain more individuals than currently present. However, consider a small population that is very dispersed and therefore partially isolated from each other. When it comes time to breed they may not be able to find a mate in time and therefore not produce any young. This is the allee effect. Low population densities mixed with isolation produces a decreased growth rate. This effect can drive many species to extinction fairly quick as it's hard to recover when a population size becomes so small so fast.

Green algae study

Submitted by mpetracchi on Thu, 10/17/2019 - 20:00

Today scientists know that actin, a protein structure in the cell, and myosin, motors running on actin structures, produce the phenomena known as cytoplasmic streaming (CS). CS is the movement of vesicles, organelles, and other cargos through the cell. This movement has been observed for a long time, however, scientists wanted to isolate exactly which structures in the cell facilitated this movement. In order to know how something works in biology, it's broken, usually in one of two ways. Either add a drug/compound to disrupt the processes, or genetically modify a specific gene. In this case, scientists used the drug approach. There were three factors scientists believed may be associated with CS, Actin, microtubules, and protein synthesis. Drugs inhibiting each respective factor were introduced. CS stopped in the Actin trial only. To verify the other two factors weren't important for CS a mix of drugs was added and in both when the actin inhibitor was introduced, CS stopped. 

Meristematic cells

Submitted by mpetracchi on Thu, 10/17/2019 - 19:44

Plants and animals owe their regenerative and replaceable properties to a class of cells known as stem cells. Plants specifically have 4 types of stem cells, also called meristems, scientists have identified and studied. First, is the shoot apical meristem (SAM). SAM's can be found at the tips of growing shoots as small translucent clumps. They're encased by a protective cover of the differentiated cells they've recently produced as to prevent any damage. Second, are auxiliary meristems. These meristems determine the sites of leaf growth and leaf categorization. If off the main shoot there is a leaf and an auxiliary meristem between the two, this leaf can be classified as a simple leaf. A shoot next to an auxiliary meristem next to a branch with leaves classifies the branched leaves as compound leaves, where each individual leaf is a leaflet. A shoot next to an auxiliary meristem next to a branch off of which smaller branches appear with leaves is classified as a doubly compounded leaf. Third, is root apical meristems (RAM). RAM's appear at root tips with a hard shell protecting the absolute tip. This is because, unlike the SAM, the roots are more susceptible to damage. Similar to the SAM's these cells grow the roots out while also producing more meristematic cells. Fourth is cambium cells. There are two cell types that fall under the cambium denomination; the cork cambium, and the vascular cambium. The cork cambium includes the bark and phloem on a plant near the outside. The vascular cambium includes some of the phloem and xylem cells on the inside of the plant.

Anthropology Part 4

Submitted by mpetracchi on Tue, 10/15/2019 - 21:05

One important difference between Egyptian and Sumerian religions is the use of animals in godly figures. Sumerian gods took the forms of human beings entirely without much reference to the animal world. In ancient Sumer the gods of people were people, thus many lessons could be learned from the hierarchy of the gods by the people. If the gods had inequality, the people should too. In ancient Egypt, the gods took the bodies of humans with the heads of animals found in Egypt. Each animal god was an interpretation of the animal in real life and had its characteristics. A falcon man was the god of the sky, the god of wisdom was a baboon man, and the god of ‘the returning land after a flood’ was a crocodile man. However different these religions may have been, they both used human figures as their gods. The Egyptians added animals, yet they kept most of the god human. I believe this was done to keep the gods familiar and relatable while still holding immense power.

Anthropology Part 3

Submitted by mpetracchi on Tue, 10/15/2019 - 17:33

Animals played key roles in Egyptian beliefs, as they expressed an ideology to support an element of Egyptian social organization. One of these animals, the ferocious crocodile, became of clear importance. This animal displayed two behaviors, one of evil and one of good, which made the crocodile god, Sobek, both feared and worshipped. When hunting, crocodiles hide in murky waters near the banks of rivers in search of their prey. Any unsuspecting woman, child, or livestock who walked nearby could become feed for the crocodile in one quick snap. Sobek may have provided the Egyptians with a sort of public service announcement to keep people away from the Nile or at least vigilant. Crocodiles were creatures to be feared. In the wild they were hunted with spears to keep populations low Why then, were crocodiles also worshipped as a form of good? As annual floods began to recede, crocodiles would be found laying in the fertile soils Egyptian farmers would later cultivate. Therefore Egyptians saw these beasts as a sign of fertile soils. A sign of good. Some crocodiles were even brought into a temple and kept as sacred animals. 


Methods Intro

Submitted by mpetracchi on Mon, 10/14/2019 - 22:39

The primary goal explores replication in a scientific setting. Studies in the scientific community are considered valid only if replicability is possible, and in order to do so, a detailed methods section must allow a peer to complete the experiment. This type of writing may be challenging as assumptions must not be taken into account as well as a balance of detail to the length of methods. 


The secondary goal of this lab seeks to identify between a difference and the factor that caused it, also known as inferences. From my experience, inferences can be made as quick as differences are noted. Therefore it may not be simple distinguishing between your inference and the difference. For example, if two different fonts are used in two figures the difference would not be the change in fonts, rather, the difference in the lettering style of the text itself. This is the observable difference. The inference then becomes ‘the fonts are different’ as it requires previous knowledge of different font styles.


Tropical Jungle PP

Submitted by mpetracchi on Wed, 10/09/2019 - 15:39

In the tropics between 10 degrees north and south of the equator resides a unique biome known as a tropical jungle. At these latitudes, consistent precipitaion rates fall which exceede 2,000 mm or 79 inches annually with two peaks around late april and october. The intertropical convergence zone (ITCZ) controls these peaks. The ITCZ is a region in the tropics with low average pressures due to the high uplift of warm air. Low air pressures generate large amounts of precipitation, as the data collected in this biome suggests. Temperatures don't vary much here, staying relatively stable around 25 degrees Celsius or 80 degrees Fahrenheit year-round. A tropical jungles stable environment, with little change in both precipitation and temperature, allows species to thrive with little to no stress or disturbance. Approximately 50% of the earth's species are present here, even though it covers only 11% of earths vegetation. However, this lack of stress or disturbance and abundance of life creates a competive enviorment requiring each species to develop a niche niche. 

Cytoplasmic Streaming

Submitted by mpetracchi on Wed, 10/09/2019 - 15:19

The discovery of cytoplasmic streaming made scientists then question, which cytoskeletal network was responsible for driving it. Scientists ingestigated two main networks, actin and microtubules. Both use protein subunits to form their polymer structures spanning the inside of cells. Actin using F-actin and microtubules using alpha/beta tubilin heterodimers. Motors on actin networks known as myosins move vesicles and organelles across the cell, similar to mircotubules which use kinesins in plant cells and kinesins/dyniens in animals cells. To understand cytoplasmic streaming, scientists needed to discover the network in charge. To do so, scientists began 'breaking' the system in plant cells using two chemicals, cytochlasin B and colchicine. When cytochlasin B interfered with the plant cell it apparead the cytoplasmic streaming process halted altogether. Washing the chemical out also confirmed the reversibility as the cells regained full cytoplasmic streaming after a short while. Scientists then decided to test colchicine in another test to determine if microtubules controlled any part of the process. Results showed no decrease in cytoplasmic streaming and therefore mircotubules may not affect this process. In order to confirm this, scientists added both chemicals to a single cell and noted similar results to previous tests. Both together inhibited cytoplasmic streaming, however, when scientists washed out cytochlasin B the cell regained function. 

Predynastic Egypt

Submitted by mpetracchi on Wed, 10/09/2019 - 14:18

The powerful and expansive Egyptian empire we know of today originally had a very humble beginning. Prior to the unification of the Egyptian people, many small groups existed across the vast nile river. Today we know there were 42 of them known as nomes. Of these nomes 22 were in 'Upper' Egypt, geograpically found in southern Egypt and 20 in 'Lower' Egypt found in the north. This upper and lower denomination comes from the formation of the nile river. The niles source flows from central Africa to the mediteranean sea, the only major river to travel south to north in the northern hemisphere. Thus the elevation change places the source higher than the delta and southern Egypt becomes 'Upper' Egypt.

The nomes in these two regions had very different cultural make-ups. Upper Egypt used strong political organizations to control their land and people. Status symbols created to revere gods and powerful figures demonstrated their wealth. They built large buildings and burial tombs as they placed great value in the afterlife. Elaborate mortuary rituals took place here in order to have the best possible chance at the life beyond ours. Shared communities grew into clustered villages surrounded by their farmland and produce.

Lower Egypt developed a culture much less involved in religious afterlifes. Their commerce was based primarily in metallurgy and long distance trade, therefore their commerce became their symbol of wealth. Afterlife carried little meaning in these societies. Instead they emphasized living the present and living this life as best they could. As for where they lived, disperesed villages grew around material pockets such as gold and lapis lazuli.

For over 2000 years this way of life ruled over this northern African land until a person named Narmer conquered and unified all 42 nomes across Egypt.


Submitted by mpetracchi on Tue, 10/08/2019 - 20:40

Across many land plants, similar cells and cell structures relating to similar functions can be identified. One of which being vascular components. A plant's vascular system can be broken down into two major groups, xylem, and phloem. Xylem are plant cells designed to transport water from the roots to the shoots via a suction pump of sorts. As the plant uses its water at a sink, place where water is used, it creates a low-pressure zone which in turn creates a pressure gradient. This gradient of high to low is what ultimately runs the movement of water in a plant. Xylem can be found near the inside of plants and in woody plants, they are actually dead. As a part of their development, they die so the plant doesn't need to spend much energy on them and it can gain structure from having many tightly packed xylem.

Phloem are the food transport cells of a plant. These are living cells whose main purpose is to facilitate the transport of sugars and foodstuffs from the leaves where sugars are created to sinks, where sugars are used, such as shoot apical meristems, root meristems, and cambial meristems. As a side, meristems are undifferentiated cells who create mature cells to replace older ones. Phloem are entirely hollow, to allow for efficient transport, however, still require 'helper' cells connected by plasmodesmata to house the necessary organelles for them to survive. Xylem and phloem work together to form the vascular system found in all vascular plants.


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