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Planarian Sensory Organs

Submitted by alexispena on Fri, 11/10/2017 - 10:36

Planarians have a nervous system composed of two main nerve chords running from their head to their tail, and connected by transverse nerves. Although basic, planarians have been shown to exhibit decision making behavior by processing external stimuli.  Planarians are able to process external stimuli by their sensory organs, eye spots and auricles. The eyespots are located on the head of the planarians and are used to detect light. The behavior in response to the change in light is called phototaxis. Planarians exhibit negative phototaxis, moving away from the light source. Auricles are on the side of the planarians head, and contribute to its triangular shape. The auricles contain chemoreceptors which respond to chemical stimuli. The auricles can play a role in finding food or the detection of changes in habitat. Both their photoreceptors and auricles help them make decisions about their environment. 

Planarian Sensory Organs

Submitted by alexispena on Thu, 11/09/2017 - 15:22

Although basic, planarians have been shown to exhibit decision making behavior. Planarians are able to process external stimuli by their sensory organs, eye spots and auricles. The eyespots are located on the head of the planarian, and are used to detect light. The behavior in response to the change in light is called phototaxis. Planarians exhibit negative phototaxis, moving away from the light source. Auricles are on the side of the planarians head, and contribute to its triangular shape. The auricles contain chemoreceptors which respond to chemical stimuli. The auricles can play a role in finding food or the detection of changes in habitat.

Body Scaling and Limb Posture

Submitted by alexispena on Tue, 11/07/2017 - 10:41

            The paper Scaling Body Support in Mammals: Limb Posture and Muscle Mechanics by Andrew Biewener, is a study on how bone structure affects the peak stresses of animals that are large and small. Peak stresses is the ratio of force to the cross sectional area of the bone, and is suggested to increase with increasing body size. This study was conducted to understand how peak bone stress and body size are independent from one another. Observation showed that smaller animals maintained a crouched position while running and larger animals align their limbs underneath their bodies, staying in an upright position. The change in limb posture could help limit stress by changing the forces acting on the muscle, but also creates limitations with maneuverability and acceleration. The study utilized videography, photography, and dissection of the various animals of different sizes to measure the forces and angles on their bodies. Measuring the effective mechanical advantage through these methods, gave quantitative data to compare between the different species of animals. There were five different species of animal used for the experiment, and the data was based on the mean value of EMA measured from each animal. 

DNA Methylation in Plants

Submitted by alexispena on Fri, 11/03/2017 - 10:23
DNA Methylation is an epigenetic mechanism that controls gene expression by adding a methyl group to DNA. In plants, methylation can occur at base pair sites CG and non CG sites, where animals can only perform it at CG sites. If DNA methylation is compromised, the loss of function can lead to the release of silenced transposable elements or repetitive DNA sequences. There are two types of DNA methylation, de novo methylation and maintanence methylation. De novo methylation occurs during embryonic or differentiation processes. It is an RNA Directed DNA methylation (RdMD) that has two plant specific RNA polymerases Pol IV and Pol V. The RdMD pathway is triggered by siRNAs. Maintenance methylation is a process to maintain methylation patterns set up by de novo methylation. Mainenance methylation can occur at CG and non CG sites; the CG site is maintained by methyltransferase1 (MET1). The chromatin remodeling factor Decrease in DNA Methylation (DDM1) also plays a role in this process. Understanding DNA methylation in plants is imporant because prior studies have evidence that DNA methylation plays a role in Hybrid vigor, the phenomenon where hybrid offspring outperform their parents. Hybrid vigor is a concept used in agriculture to produce more main crops such as corn. 
 
 

DNA Methylation in Plants

Submitted by alexispena on Wed, 11/01/2017 - 23:15
•DNA Methylation is an epigenetic mechanism that controls gene expression by adding a methyl group to DNA (1)
•Methylation can occur at CG and non CG sites in plants
•Loss of function leads to the release of silenced transposable elements or repetitive DNA sequences
•There are two types of DNA methylation
De Novo Methylation: Methylation that occurs during the embryonic or differentiation processes. (5) It is RNA Directed DNA Methylation (RdMD) that has two plant specific RNA polymerases Pol IV and Pol V. (4) 
Maintenance DNA Methylation: a process to maintain methylation patterns set up by  de novo methylation. Maintenance methylation can occur at CG or non CG sites,  CG site methylation is maintained by Metyltransferase 1 (MET1). The chromatin remodeling factor Decrease in DNA Methylation (DDM1) plays a role in this process.(2) 

Basic Principles of Movement

Submitted by alexispena on Mon, 10/30/2017 - 20:05

Muscles can be thought of in two types, slow twitch and fast twitch. Slow twitch muscles are used for slow aerobic movement like walking.They are smaller in diameter, and are bright red. Fast twitch muscles are used for bursts of speed or strength. They are larger in diameter, meaning they are stronger, are lighter in color, and are prone to fatigue. Fast twitch muscles can be built by heavy lifting and strength training, but it will not help with endurance. Vertebrate muscle systems are composed of a combination of muscles, bones, and tendons. The tendons attach the muscles to the bone. 

Locomotion Notes

Submitted by alexispena on Fri, 10/27/2017 - 13:00

Many organisms big and small locomote, move about under one's own power. Locomotion is energetically expensive, the energy used to measure locomotion can be expressed in units of mass, distance, and time in terms of kinetic energy. Animals with muscels use them to produce mechanical power, which consumes ATP. Even animals without muscles still use ATP for movement. The overall efficiency of any biological movement is expressed as the ratio of mechanical work produced to chemical energy consumed, locomotion is not efficient. The efficiency of vertebrate muscle is about 25%, the other 75% of chemical energy is lost as heat. 

Animal Locomotion

Submitted by alexispena on Fri, 10/27/2017 - 12:50

The paper "Scaling Body Support in Mammals: Limb Posture and Muscle Mechanics" by Biewener reviews how different sized animals minimize stress on their joints and muscles due to their body posture.  Peak stresses, the ratio of force to a cross sectional area in a bone, should increase with increasing body size, but in nature peak bone stress is independent of body size. This is because the locomotive limb posture is different between small and large animals. Small animals run in a crouching position, where as large animals are in an upright position, with their limbs straight underneath their body. The change in limb posture in large animals comes with a trade off, it limits the peak stresses but the animals lose maneuverability and acceleration. 

Review for Animal Movement

Submitted by alexispena on Sun, 10/22/2017 - 17:43

Taxonomy of Movement

  • Home range is the area an animal typically move within to obtain necessary resources for reproduction and survival
    • Home range size depends on body mass and diet (i.e. large carnivores have a larger home range than a large or small herbivore) and habitat type/quality
  • Stasis is when some animals never move or move only in gamete or larval stage
    • Most animals spend large portions of their day static and some spend months or years (i.e. hibernation)
  • Station Keeping: most movements that determine the home range of an animal or are resource directed movements. Movements that keep an animal within its home range.
    • Kinesis: simple changing of movement no consistent relationship to stimulus
      • Random, aimless movement
      • i.e. Sage grass males put on elaborate displays, females are not interested
    • Taxes: directed movement where the long axis of body shows a consistent relationship with stimulus
      • A fly that is focused on a light
    • Foraging: searching movement that’s readily interrupted by encounter w/resources
      • It can be extensive
    • Commuting: round-trip regular movements within the home range
      • Vertical commuting of copepods
    • Territoriality behavior: movement made to maintain or defend a territory
      • Scent marking
    • Ranging: Exploratory movements outside of home range often to look for new habitats, “dispersal”. The movement stops when new resources/habitat are encountered.
      • Term dispersal is problematic because individuals cannot disperse 

Legend for Sabaody Archipelago

Submitted by alexispena on Fri, 10/20/2017 - 15:10

Figure 1: Graphical Analysis of Data from Sabaody Archipelago 

This figure is a graphical analysis of the data from sabaody archipelago to visualize correlations between GPA, hours slept per week, hours studied  per week, and gender. The most relevent trends in the graphs are visualized in the hours slept versus GPA and hours studied versus GPA. In the hours slept versus GPA graph both males and females had a positive correlation between hours slept and their GPA. In the hours studied versus GPA graph, females had a positive correlation between the hours studied and their GPA. Men did not exhibit a correlation. The outliers in the data set with an O for gender, 100 hours for hours studied per week, and 5 hours for hours slept per week were removed to make more concise graphs. 

 

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