Hungry and satiety: a deeper look.

It’s natural to feel hungry when you need to refuel your body, or to feel satisfied when you are refueled.  But think deeper, how are we able to feel hunger and satiety?  Various organs, chemicals and mechanisms contribute to the feeling you get when either hungry or satisfied.

Hormones signal the satiety (satisfied)  part of the brain, depending on whether the body needs nutrition, or whether it’s satisfied.  The hormone called Ghrelin, sometimes known as the “hungry hormone” is the chemical released by the stomach when the stomach is empty, and it is continued to be released until the stomach is stretched out or satisfied.  When you miss a meal, and begin to feel hungrier and hungrier, it is when ghrelin is collectively released by the stomach.

What about the feeling of satiety?  The hormone insulin, is released by pancreas when blood sugar is too high, and it actually suppresses the appetite.  Figuratively, insulin is telling the brain that it has consumed too much sugar for now, and sending signals for it to not consume anymore until further notice.

There is another hormone called Leptin.  Leptin is released by adipose (fat) tissue, and this chemical also suppresses appetite.  Levels of leptin are actually decreased with loss of weight, which could explain why it is hard to maintain a diet with the intent to lose weight.

Another important hormone is Peptide YY, or PYY.  PYY is secreted by the small intestine when the organism finishes consuming a meal.  PYY counteracts the effects of ghrelin, and suppresses the appetite.

In conclusion, hunger and satiety are much more than just a growl  in the stomach.  There are a lot of chemicals and mechanisms that signal the brain and tell it what the body needs.



What does it mean for a creature to be intelligent?

On a general day-to-day basis, you encounter a variety of people, each who have a different impact on you.  One of the main factors that determines this impact is their overall intelligence.  What is meant by intelligence?

According to the Oxford dictionary, intelligence is defined as, the ability to acquire and apply knowledge and skills.  So thus, for a creature to be intelligent, that creature must possess the ability to acquire knowledge and skills, and apply them in relevant circumstance.  There are many different classes of animals that have intelligent behavior, and it is a fascinating topic.

One of the most intelligent group of animals are elephants.  Elephants are known for their incredible memory, and they are also known to show sympathy when members of their herd die.  Their sympathetic nature is very human-like.  It is incredible that these animals possess that kind of caring nature.  They are able to learn and use creative skills, such as painting.  They have been significant in agriculture, especially in Africa in ancient times.  They possess unique strength and intelligence, which is fascinating to mankind, but also helpful in the wild.

And probably the most intelligent group in the animal kingdom, are primates, specifically the clade simians.  This group includes monkeys and apes, some of which have similar DNA to humans.  Some species of simians can actually teach each other basic skills, that vary among their different tribes.  Some apes are able to recognize individuals in their group, and they understand the levels of authority within their own community.  They are able to utilize tools in the wild, and also while in captivity.  Most apes are able to communicate to humans, via sign language, which is truly an amazing ability.

The intelligence of animals is a topic that we do not, and really cannot fully understand, but it has been studied for centuries, and will continue to amuse us as we make new discoveries.

Should all the species in phylum Arthropoda be classified under one group?

Arthropoda is the largest phylum in the world, with over 1,000,000 known species.  This group of creatures possess multiple common characteristics that justify them to be classified in the same group.

On the Linnaean scale of classification, phylum is the classification directly below the kingdom classification.  Among arthropods, there are multiple different classes and sub-phyla. Some of these include: crustaceans, insects, and arachnids.  Some common classes of arthropods are lobsters, crabs, beetles, winged insects, etc. Sub-phylum, chelicerata, contains the class arachnid, which includes spiders, ticks and scorpions.

There is tremendous diversity within this phylum, however, they all share a basic body plan. There are variations among different classes and species (and especially the sub-phylum arachnids), but they all follow one basic blueprint.  Each further classification is specialized with different vices, but still share basic characteristics.  What is this body plan? Arthropods have a full body exoskeleton, and jointed limbs, and three separate body cavities: a head, a thorax, and an abdomen. –With the exception of arachnids, that have a joined head and thorax, called a cephalothorax.

As many species as there are within this phylum, one can imagine the incredible diversity of arthropods.  There is so much detail we already know, and there are so many details mankind has yet to discover.

All these species being classified into one group poses the question: should they all be classified in just one group?  Yes, they should all be classified together.  Why?  Because they all share the same basic structure, and engage in similar behaviors.  This body plan gives them similarity, and even though the basic structure varies tremendously, the species all have similar behaviors and metabolic processes.  The body blue print of arthropods preserves the relationship between all the species within the phylum.

Chordates, and how they are different from Vertebrates.

What is a chordate? How are vertebrates different from chordates?

A chordate is a member of the animal kingdom, and categorized in the phylum Chordata.  Chordates have several characteristics that define them, and set them apart from all other animals.  Some of these traits are only present during embryonic development, but nonetheless, they do serve a crucial purpose within the organism.

Chordates have a notocord, which is essentially a long, flexible rod placed within the organism between dorsal nerve cord and the digestive tract.  The notochord serves many purposes, as it is built out of stiff, fibrous tissues.  Aquatic animals push muscle against this to help them swim, for example.

Chordates also have a dorsal nerve cord, which is a hollow nerve cord.  This dorsal nerve cord, in a human, becomes the spinal cord and brain after the process of embryonic development.

Another characteristic of chordates is the pharyngeal cleft.  The pharynx is the head/neck region of the animal right behind the mouth.  The pharyngeal cleft is a cleft, or pouch like structure in the pharynx region.  The form the pharyngeal cleft takes, and the function it carries out, depends on whether the animal is terrestrial or aquatic.

Chordates also have a muscular tail.  This tail may only be visible during embryonic development, but it is an essential trait during embryonic development.  Depending on the species, it may shrink if the species no longer depends on it.  The muscular tail extends beyond the digestive tract, and for aquatic chordates especially, this tail is important to propel the animal.

How are chordates different from vertebrates?  The vertebrate definition is a craniate with a backbone.  What is a craniate?  Craniates are all the members of the phylum chordata that have a head.  A head contains a brain at the front end of the dorsal nerve chord, as well as the common sensory organs such as nose, eyes, ears, mouth.  There are actually many invertebrates that have a head, however, a craniate is exclusively a chordate with a head.

To conclude, a vertebrate is a chordate, if, and only if, the chordate is a craniate with a backbone.  A chordate must possess a head and backbone in order for it to be a vertebrate.


(Biology, Lesson 100 essay.)


Soil is much more than just “dirt” that holds up the plant.

“Soil is just dirt to hold the plant up.”  — This is a statement that I, and many other individuals can easily disagree with.  However, it seems that a majority of the population agrees with this statement. It is actually fairly easy to adopt the idea of soil being just dirt, intended only to support the plant, but soil is much more than that.

It is easy to overlook soil, and how crucial it is to all levels of life, because it’s not something we notice on a day-to-day basis.  Plants, bodies of water, animals, etc., perform events crucial to the environment that we can, for the most part, see and feel.  The soil, however, is essentially just the dirt under our feet.  If an individual does not want to go into the details of the complexity of soil,  it is easy to adopt the opinion of it being simply dust underfoot.

Soil has so much complexity, that someone could dedicate their entire life to studying it through pedology, or edaphology, and still only cover a small portion of study.

Why is soil so important?  Aside from water, what do animals and humans need for survival? Nutrition. Some of their nutrition comes from other animals, but those animals have to eat something.  Plants support the entire animal kingdom,either by primary or secondary consumption.

What feeds the plants? Plants utilize energy from the sun to perform photosynthesis, and this is their main nutrient, but there are nutrients in the soil that act as supplements for the plant, and affect the production of the plant. Like people, plants benefit from supplements in their nutrition.

There are several biotic and abiotic factors that affect the characteristic of the soil and will determine the plants ability to grow.  Soil supports plants, that’s a mutual opinion, but soil does more than just that.

There are many layers of soil that perform important functions, however the most important of these is the layer of top soil.  The top soil is the layer from which plants absorb minerals and receive benefits from other living organisms.

The soil in an ecosystem is important, it affects plant growth, which then significantly affects the population of other animals and organisms. Soil also supports many organisms such as earthworms, that need the soil environment to survive.  Soil does not just support plants, it supports the entire ecosystem.


Factors that Delay Reproduction of a Plant and How They are Actually Helpful to the Plant Species.

A perfectly healthy seed may not germinate for a long time; months, or possibly even years.  There are multiple factors that determine the timing of germiantion.  Through the beginning of the life cycle of a plant; the period between pollination to germination, there are several factors that essentially slow down, or delay the reproduction process of a plant.  Most of these factors, that slow or delay the process, are actually helpful to the plant species.

How do these delaying factors actually help the seed?  Seed germination requirements essentially help the seed grow under ideal conditions.  The seed does not usually germinate until the conditions meet the requirements.

One of the biggest factors that delays seed germination is season.  There are different plant species that can thrive in the different seasons throughout the year, however, one given plant species that thrives in spring may not be able to survive through winter. This factor slows the germination of a seed, and if the seed somehow germinates anyway, the chance of survival is low.  The limitations of the seasons are ultimately beneficial to the plant species.

Another significant germination-delaying factor is food/water supply.  If there is not enough nutrition in the environment, the plant will struggle, and may not survive, thus this is an important limiting factor.  Germination should not happen if there is not a stable food supply.  If there is lack of water in the environment, like nutrition, the plant has a low risk of survival.  However, unlike nutrition, too much water can also be harmful to the plant species and can effect the timing of germination.

These are a small few of the many factors that delay or slow down the germination of a seed, there are many more factors that play an equally important role.

How the Calvin cycle indirectly depends on light.

Photosynthesis is the process through which plants (and some other organisms), covert light energy from the sun into chemical energy that can be utilized by other organisms.  In order to carry out this complex process, cells are equip with specialized cells.  There is a cell wall made of cellulose, within, there are membrane closed organelles, and in addition, there is another specialized organelle called a chloroplast.  The chloroplast is the feature of the plant cell  that allows the plant to carry out photosynthesis.

In photosynthesis, there are two major stages, the first being light-dependent reactions and the other being the Calvin cycle, both take place within the chloroplast.  The light dependent reactions occur before the Calvin cycle takes place.  While the Calvin cycle is not actually part of the light-dependent reactions of photosynthesis, the Calvin cycle does indirectly depend on light.

The light-dependent reactions, as stated above, occur prior to the Calvin cycle.  The Calvin cycle actually requires the use of the products from the light dependent reactions.  Products include ATP (adenosine triphosphate), NADPH (nicotinamide adenine dinucleotide phosphate-oxidase), and also o2 that is released into the atmosphere.  There are energy and material requirements of the Calvin cycle, which rely on light-dependent reactions as their suppliers.

There are 3 phases of the Calvin cycle: carbon fixation, reduction, regeneration of co2 acceptor.  With all three phases, there is an overall “cost” of the Calvin cycle.  The Calvin cycle needs outside resources, these resources are produced by the light-dependent reactions.  These “costs” of resources include, 3 co2, 9 ATP, and 6 NADPH.  Co2 comes from the atmosphere, however, without light-dependent reactions, the Calvin cycle has no way to obtain the required ATP and NADPH.

The Calvin cycle is indirectly dependent on light because without the light-dependent reactions, and their products, the Calvin cycle cannot take place.

The challenges of Taxonomy. Is Taxonomy necessary?

Taxonomy is the science of naming and classifying living organisms.  Systematics are the use of data to determine the relationships between different species.  Systematics guide the process of taxonomy, which classify all the living organisms. This is a complex process due to the fact that there are so many living organisms in the world’s overall biomass.

In early taxonomy, there were two kingdoms in which organisms were classified: plants, and animals.  However, there were organisms that possessed characteristics of both plants and animals.  This kingdom of two, was later expanded to include protists, (organisms that possessed the characteristics of animals and plants).  However, this did not include a category for every living organism.  Thus 5 animal kingdoms were developed: plants, animals, fungi, protists, and monera.

Monera, which the single celled prokaryotic classification,posed an issue.  Prokaryotic cells are more similar to eukaryotic cells, than to other prokaryotic cells.  For this and other reasons, monera has become obsolete.

These kingdoms are divided into three domains: bacteria, archaic, and Eukaryota.  (Monera possesses characteristics of more than one domain; another reason why it is obsolete.)

This system has flaws and errors, but at this point, it is the only method scientists have been able to use, somewhat effectively.  A biologist’s classification should not necessarily be taken as an absolute inviolable truth, because there are still many errors in the system.  A biologist’s classification should be considered and also analyzed, with an open-critical mind.

For now, this system is both necessary and important.  Systematics and taxonomy have flaws, but they are an essential means of organization.  This system makes the work of a biologist easier, when researching, or discovering a new species.  Perhaps a better method, with more accuracy will eventually be developed, but for now, biologist’s rely on systematics and taxonomy.

The Impacts of Mutualism, Predation, and Interspecific Competition.

Explain how mutualism, predation, and inter-specific competition are different from each other. How does each one affect the interacting populations of the two species?

Mutualism, predation, and inter-specific competition, are all categorized as inter-specific interactions between two species.  Each one of these include an interaction between two or more species in the same environment.  In each of these interactions, each species is either harmed or benefited by the type of interaction.

  1. Mutualism is when two organisms work together in a way that is beneficial (or maybe even essential) for both parties.  An example of this is the relationship between bumblebees and flowers.  The bumblebee collects nectar, which is the essential source from which the bumblebee makes their food.  In the process of collecting nectar, the bee flies from flower to flower spreading pollen, helping the flowers in an area to pollinate, which is essential process for the reproduction of the flower.  This is an interaction between two species in which both species benefit.
  2. Predation is the involvement of two organisms, when one species (the predator) kills and eats another species (the prey) that is subordinate on the food chain.  An example of this is a coyote, catching and feeding on a rabbit.  The coyote needs the nutrition of the rabbit, it is essential for survival.  If there were not predators such as coyotes to prey on rabbits, the rabbit population would expand to an unmanageable number.  The predator benefits from this interaction at the expense of the prey, who only receives harm, or in this case, death.
  3. Inter-specific competition is when two different species compete for the same resource in a given ecosystem.  Predators, herbivores, and any type of plant encounter this issue.  An example is when the main diet of a hawk in a given ecosystem is a rabbit, but coyotes in that same ecosystem are supported by rabbits.  Both have a limited supply due to the pressure on the rabbit population caused by both species.  Neither species really benefits from this.

Savanna vs. Tropical rain forest.

From Wikipedia, “A biome /ˈbm/ is a community of plants and animals that have common characteristics for the environment they exist in.”  There are two categories of biomes, terrestrial biomes and aquatic biomes.  In these two general categories there is a wide variety of biomes.  In this assignment, I have selected, and will contrast two terrestrial biomes: the savanna, and the tropical rain forest.

A savanna is an open grassland, the trees in a savanna are sufficiently spread so that they do not create a canopy blocking direct sunlight to the soil.  However, this does not mean that they do not have high tree density, the trees are simply more regularly spaced than in tropical  forests.  Savanna covers about 20% of the earth’s surface, and despite the dryness, the savanna can support a lot of life.  Grazing or browsing animals are common inhabitants of a savanna.  The temperature year-round generally averages in the high 70’s (68-86 F), which is helpful to the organisms living there.  One of the challenges that faces the inhabitants of a savanna, is the danger of wildfires, which are common in a savanna.

Unlike the savanna, tropical rain forests have a canopy of trees that almost entirely blocks direct sunlight to the soil, this provides opportunity for organisms very different from those who occupy a savanna.  Tropical rain forests do not encounter a dry season, and encounter a lot of rain (avg. of 60 mm per month) year round.  Tropical rain forests are withing 10 degrees (north or south) of the equator.  The temperature is fairly consistent year round- rarely getting above 93 degrees Fahrenheit, and rarely getting below about 68 degrees Fahrenheit, which is pretty consistent year round, however, not as consistent as the average savanna temperature range.

The two biomes are significantly different from one another and the inhabitants of each face different challenges every day.  The organisms in each biome are equip to survive the conditions of  that biome.