Gastrulation is one of the most important phases in the life of multicellular organisms. Blastula, a single layered cell structure converts into trilaminar structure with three layers, known as gastrula. The word ‘gastrula’ means stomach, since stomach (archenteron) is the first thing formed during gastrulation.
There are basically three main events that occur during gastrulation. These are as follows;
1. Formation of three primary germ layers.
2. Basic body plan and body axes are established. Three embryonic axes are formed i.e. dorsal-ventral, posterior-anterior and left-right.
3. Gastrulation movements result in new neighbourhood of cells.
Formation of germ layers is the first step towards multicellular organisms. It establishes division of tissue types. Diploblastic organisms, such as coelenterates, have two germ layers (ectoderm and endoderm), whereas triploblastic organisms, which include all higher animals, have three germ layers (ectoderm, mesoderm and endoderm). These germ layers are often termed as leaves with ectoderm being the outer leaf, mesoderm being the middle leaf...
The results from the experiments supported the hypothesis that the batoid pelvic girdle shape correlated with the type of locomotion. They found that the form of locomotion utilized by the batoid had a greater determining factor on the shape of the pelvic girdle compared to the phylogeny. An important discovery of this experiment showed that the shape of the pelvic girdle of a batoid can be used to predict the swimming and punting mode, and the order to which the vertebrate
The braine is part of three divided that represent front, back and saggital planes which divides the left from right of braine. A horisontal planes divides the braine in to top and bottom position.
Human skin is a multi-layered structure. It is generally divided into two layers, the epidermis and the dermis. Below the dermis a subcutaneous fat layer is found. The epidermis can be further divided into several sub-layers. These are the stratum corneum, the stratum lucidum, the stratum granulosum, the stratum spinosum, and the stratum germinativum. The stratum germinativum is usually referred to as the basal layer.
All references and resources are taken from the Public Library of Science, Biology March 2004 issue and from Science March 16, 2004
Retrieved 14 May 2014, from http://www.teachpe.com/a_level_analysis/movement_analysis_webpage.html. Thibodeau, G., & Patton, K. (1993). "The Species of the World. " Chapter ten: Anatomy of the muscular system. In Anatomy and Physiology (1st ed., p. 252).
Mink Intro – External Anatomy Overview. (n.d.). mreroh.com . Retrieved May 27, 2014, from http://www.mreroh.com/student/apdocs/Dissection/Intro%20-%20External%20Anatomy.pdf
Vasconcelos, O., Rodrigues, P., Barreiros, J. & Jacobsohn, L. (2009). Laterality, developmental coordination disorders and posture. In L. P. Rodrigues, L. Saraiva, J. Barreiros & O. Vasconcelos (Eds.) Estudos em desenvolvimento motor da criança II (pp.19-26). Escola Superior de Educação, Instituto Politécnico de Viana do Castelo.
Meiosis, also called reduction division, is a distinct type of cell division that is essential for sexual reproduction to occur. It is one in which two successive divisions of diploid cell occur thereby producing four genetically different haploid daughter cells, also called gametes, each with half the number of chromosomes and thus, half the total amount of genetic material as compared to the amount before meiosis began. Interphase precedes meiosis and thus, paves the way for meiosis to eventuate as the cell’s DNA replicates in the S phase yielding corresponding, identical chromosomes. Interphase sparks the marvelous process of meiosis that allows variation to transpire within the organisms it occurs, hence, giving rise to millions of organisms with unique aspects unlike any other on Earth. Because meiosis is a form of sexual reproduction itself, it is the means through which gametes are produced, each with a reduced number of chromosomes, so that when two gametes fuse during fertilization, not only do they form a diploid zygote with 46 chromosomes, but also have manifested differing features due to the rearrangement (crossing-over) of chromosomes.
This stage is divided into six substages are Simple Reflexes , Primary Circular Reactions , Secondary Circular Reactions , Coordination of Secondary Schemes , Tertiary Circular Reactions and Invention of New Means through Mental Combinations. These are described as : The first substage covers the first month after birth , it is dominating by the assimilation of sources of stimulation of inborn reflexes such as grasping or visual tracking (Rathus, S., & Longmuir, S., 2011 , p.81). The second substage is defined as primary circular reactions is focus on the infant’s own body rather than on the external environment . It lasts from about 1 to 4 (-in APA write out numbers under ten) month of age and is characterized by the beginning of the ability to coordinate various sensorimotor circular reaction(s). (space)In this (word missing) the infants focus changes from focusing on themselves to focusing on the external environments and this includes objects (Rathus, S., & Longmuir, S., 2011 , p.82) . During the fourth stage infants tends to imitate gestures and sounds that they had previously ignored and they also coordinates to attain a specific goals , for example trying to picking up the objects (Rathus, S., & Longmuir, S., 2011 ,
The cytoskeleton is a highly dynamic intracellular platform constituted by a three-dimensional network of proteins responsible for key cellular roles as structure and shape, cell growth and development, and offering to the cell with "motility" that being the ability of the entire cell to move and for material to be moved within the cell in a regulated fashion (vesicle trafficking)’, (intechopen 2017). The cytoskeleton is made of microtubules, filaments, and fibres - they give the cytoplasm physical support. Michael Kent, (2000) describes the cytoskeleton as the ‘internal framework’, this is because it shapes the cell and provides support to cellular extensions – such as microvilli. In some cells it is used in intracellular transport. Since the shape of the cell is constantly changing, the microtubules will also change, they will readjust and reassemble to fit the needs of the cell.
This is the embryonic period, which occurs three weeks after conception and lasts until the eighth week. During the fourth week, the shape of the head begins to form, along with the formation of the eyes, mouth, nose, and mouth. Through the fifth and eighth week the lower body develops, as the legs and arms appear. After the embryonic stage, the fetal stage begins, which is during the ninth week through birth, where the fetus has a physical appearance distinctive to human features compared to when it was an embryo. At birth, one of the earliest signs of motor development is its first reflexes as a newborn coming out the mother’s womb. Newborns reflexes are not learned, rather they are born with these reflexes and act instinctively to protect itself in its first few months of life. At this point both the physical and motor development is starting to develop naturally at the same
Evolutionary developmental biology (evo-devo) was instituted in the early 1980s as a distinctive field of study to characterise the new synthesis of evolution hypothesis (Müller, 2007). Evo-devo is regarded as a new rule in evolutionary biology and a complement to neo-Darwinian theories. It has formed from the combination of molecular developmental biology and evolutionary molecular genetics; their integration has helped greatly to understand both of these fields. Evo-devo as a discipline has been exploring the role of the process of individual development and the changes in evolutionary phenotype, meaning the developmental procedure by which single-celled zygotes grow to be multicellular organisms. Alterations in the developmental program frequently cause differences in adult morphology.
middle of paper ... ... World Book Inc, 2000. Davis, Lloyd S. and John T Darby. Penguin Biology. San Diego: Academic Press, Inc., 1990.
As infants grow in size their motor skills improve through body movements. Through fine and gross motor skills infants learn to master movements, such as sitting, crawling, standing, and walking. These sensory and motor skills follow a genetic timetable, which is influenced...