1.
Human embryogenesis
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Human embryogenesis is the process of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, human development entails growth from a zygote to an adult human being. Fertilisation occurs when the cell successfully enters and fuses with an egg cell. The genetic material of the sperm and egg then combine to form a single cell called a zygote, embryogenesis covers the first eight weeks of development, at the beginning of the ninth week the embryo is termed a fetus. Human embryology is the study of development during the first eight weeks after fertilisation. The normal period of gestation is nine months or 38 weeks, the germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus. The germinal stage takes around 10 days, during this stage, the zygote begins to divide, in a process called cleavage. A blastocyst is then formed and implanted in the uterus, embryogenesis continues with the next stage of gastrulation, when the three germ layers of the embryo form in a process called histogenesis, and the processes of neurulation and organogenesis follow. In comparison to the embryo, the fetus has more recognizable external features, the entire process of embryogenesis involves coordinated spatial and temporal changes in gene expression, cell growth and cellular differentiation. A nearly identical process occurs in species, especially among chordates. Fertilization takes place when the spermatozoon has entered the ovum. This usually takes place in the ampulla of one of the fallopian tubes, the 46 chromosomes undergo changes prior to the mitotic division which leads to the formation of the embryo having two cells. Successful fertilization is enabled by three processes, which act as controls to ensure species-specificity. The first is that of chemotaxis which directs the movement of the sperm towards the ovum, secondly there is an adhesive compatibility between the sperm and the egg. The entry of the sperm causes calcium to be released which blocks entry to other sperm cells, a parallel reaction takes place in the ovum called the zona reaction. This sees the release of granules that release enzymes which digest sperm receptor proteins. The granules also fuse with the membrane and modify the zona pellucida in such a way as to prevent further sperm entry. The beginning of the process is marked when the zygote divides through mitosis into two cells
2.
Child
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Biologically, a child is a human being between the stages of birth and puberty. The legal definition of child generally refers to a minor, otherwise known as a younger than the age of majority. There are many issues that affect children, such as childhood education, bullying, child poverty, dysfunctional families, child labor, hunger. Children can be raised by parents, by fosterers, guardians or partially raised in a day care center. The United Nations Convention on the Rights of the Child defines child as a human being below the age of 18 years unless under the law applicable to the child and this is ratified by 192 of 194 member countries. Biologically, a child is generally anyone between birth and puberty, some English definitions of the word child include the fetus. In many cultures, a child is considered an adult after undergoing a rite of passage, recognition of childhood as a state different from adulthood began to emerge in the 16th and 17th centuries. Society began to relate to the not as a miniature adult but as a person of a lower level of maturity needing adult protection, love. This change can be traced in paintings, In the Middle Ages, in the 16th century, images of children began to acquire a distinct childlike appearance. From the late 17th century onwards, children were playing with toys. Every child goes through stages of social development. An infant or very young child will play alone happily, if another child wanders onto the scene, he or she may be physically attacked or pushed out of the way. Next, the child can play with another child, gradually learning to share, eventually, the group grows larger, to three or four children. By the time a child enters kindergarten, he or she can join in. Children with ADHD and learning disabilities may need help to develop social skills. The impulsive characteristics of an ADHD child may lead to poor peer relationships, children with poor attention spans may not tune into social cues in their environment, making it difficult for them to learn social skills through experience. The age at which children are considered responsible for their society-bound actions has changed over time. In Roman times, children were regarded as not culpable for crimes, in the 19th century, children younger than seven years old were believed incapable of crime
3.
Death
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Death is the cessation of all biological functions that sustain a living organism. Bodies of living organisms begin to decompose shortly after death, other concerns include fear of death, necrophobia, anxiety, sorrow, grief, emotional pain, depression, sympathy, compassion, solitude, or saudade. The potential for an afterlife is of concern for some humans, the word death comes from Old English deað, which in turn comes from Proto-Germanic *dauthuz. This comes from the Proto-Indo-European stem *dheu- meaning the Process, act, when a person has died, it is also said they have passed away, passed on, expired, or are gone, among numerous other socially accepted, religiously specific, slang, and irreverent terms. Bereft of life, the person is then a corpse, cadaver, a body, a set of remains, and when all flesh has rotted away. The terms carrion and carcass can also be used, though more often connote the remains of non-human animals. As a polite reference to a person, it has become common practice to use the participle form of decease, as in the deceased. The ashes left after a cremation are sometimes referred to by the neologism cremains, senescence refers to a scenario when a living being is able to survive all calamities, but eventually dies due to causes relating to old age. Almost all animals who survive external hazards to their biological functioning eventually die from biological aging, some organisms experience negligible senescence, even exhibiting biological immortality. These include the jellyfish Turritopsis dohrnii, the hydra, and the planarian, unnatural causes of death include suicide and homicide. From all causes, roughly 150,000 people die around the world each day, physiological death is now seen as a process, more than an event, conditions once considered indicative of death are now reversible. Where in the process a dividing line is drawn between life and death depends on factors beyond the presence or absence of vital signs, in general, clinical death is neither necessary nor sufficient for a determination of legal death. A patient with working heart and lungs determined to be dead can be pronounced legally dead without clinical death occurring. As scientific knowledge and medicine advance, formulating a precise definition of death becomes more difficult. The concept of death is a key to understanding of the phenomenon. There are many approaches to the concept. For example, brain death, as practiced in medical science, One of the challenges in defining death is in distinguishing it from life. As a point in time, death would seem to refer to the moment at which life ends, determining when death has occurred requires drawing precise conceptual boundaries between life and death
4.
Attachment theory
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Attachment theory is a psychological model that attempts to describe the dynamics of long-term and short-term interpersonal relationships between humans. However, attachment theory is not formulated as a theory of relationships. It addresses only a specific facet, how human beings respond within relationships when hurt, separated from loved ones, essentially all infants become attached if provided any caregiver, but there are individual differences in the quality of the relationships. Fathers or any other individuals, are likely to become principal attachment figures if they provide most of the child care. In the presence of a sensitive and responsive caregiver, the infant will use the caregiver as a base from which to explore. It should be recognized that even sensitive caregivers get it right only about 50 percent of the time and their communications are either out of synch, or mismatched. There are times when parents feel tired or distracted, the telephone rings or there is breakfast to prepare. In other words, attuned interactions rupture quite frequently, but the hallmark of a sensitive caregiver is that the ruptures are managed and repaired. Attachments between infants and caregivers form even if this caregiver is not sensitive and responsive in social interactions with them, infants cannot exit unpredictable or insensitive caregiving relationships. Instead they must manage themselves as best they can within such relationships, early patterns of attachment, in turn, shape — but do not determine — the individuals expectations in later relationships. Four different attachment classifications have been identified in children, secure attachment, anxious-ambivalent attachment, anxious-avoidant attachment, and disorganized attachment. Attachment theory has become the dominant theory used today in the study of infant and toddler behavior and in the fields of infant mental health, treatment of children, and related fields. Secure attachment is when children feel they can rely on their caregivers to attend to their needs of proximity, emotional support and it is considered to be the best attachment style. Anxious-ambivalent attachment is when the infant feels separation anxiety when separated from the caregiver, anxious-avoidant attachment is when the infant avoids their parents. Disorganized attachment is when there is a lack of attachment behavior, in the 1980s, the theory was extended to attachment in adults. Attachment applies to adults when adults feel close attachment to their parents, within attachment theory, attachment means a biological instinct in which proximity to an attachment figure is sought when the child senses or perceives threat or discomfort. Attachment behaviour anticipates a response by the attachment figure which will remove threat or discomfort. Such bonds may be reciprocal between two adults, but between a child and a caregiver these bonds are based on the childs need for safety, security and protection, paramount in infancy, in the most complex organisms, instinctive behaviors may be goal-corrected with continual on-course adjustments
5.
Psychosexual development
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Each stage – the oral, the anal, the phallic, the latent, and the genital – is characterized by the erogenous zone that is the source of the libidinal drive. He argued that adult neurosis often is rooted in childhood sexuality, sexual infantilism, in pursuing and satisfying his or her libido, the child might experience failure and thus might associate anxiety with the given erogenous zone. e. The tendency to place objects in the mouth, the id dominates, because neither the ego nor the super ego is yet fully developed, and, since the infant has no personality, every action is based upon the pleasure principle. Nonetheless, the ego is forming during the oral stage, two factors contribute to its formation, in developing a body image, he or she is discrete from the external world. Weaning is the key experience in the oral stage of psychosexual development. In the case of too little gratification, the infant might become passive upon learning that gratification is not forthcoming, the style of parenting influences the resolution of the id–ego conflict, which can be either gradual and psychologically uneventful, or which can be sudden and psychologically traumatic. If the child obeys the id, and the yield, he or she might develop a self-indulgent personality characterized by personal slovenliness. If the parents respond to that, the child must comply, but might develop a sense of self, because it was the parents will, and not the childs ego. The third stage of development is the phallic stage, spanning the ages of three to six years, wherein the childs genitalia are his or her primary erogenous zone. In the phallic stage, a boys decisive psychosexual experience is the Oedipus complex and this psychological complex derives from the 5th-century BC Greek mythologic character Oedipus, who unwittingly killed his father, Laius, and sexually possessed his mother, Jocasta. Analogously, in the stage, a girls decisive psychosexual experience is the Electra complex. The boy focuses his libido upon his mother, and focuses jealousy, Electra, Whereas boys develop castration anxiety, girls develop penis envy that is rooted in anatomic fact, without a penis, she cannot sexually possess mother, as the infantile id demands. As a result, the girl redirects her desire for sexual union upon father, thus, moreover, after the phallic stage, the girls psychosexual development includes transferring her primary erogenous zone from the infantile clitoris to the adult vagina. Freud thus considered a girls Oedipal conflict to be more intense than that of a boy, resulting, potentially. Psychologic defense, In both sexes, defense mechanisms provide transitory resolutions of the conflict between the drives of the Id and the drives of the Ego. The first defense mechanism is repression, the blocking of memories, emotional impulses, in a boy, a phallic-stage fixation might lead him to become an aggressive, over-ambitious, vain man. The genital stage affords the person the ability to confront and resolve his or her remaining psychosexual childhood conflicts, as in the phallic stage, the genital stage is centered upon the genitalia, but the sexuality is consensual and adult, rather than solitary and infantile. Hence, the stage proved controversial, for being based upon clinical observations of the Oedipus complex
6.
Sea urchin
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Sea urchins or urchins, archaically called sea hedgehogs, are small, spiny, globular animals that, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. About 950 species of echinoids inhabit all oceans from the intertidal to 5,000 metres deep, the shell, or test, of sea urchins is round and spiny, typically from 3 to 10 cm across. Common colors include black and dull shades of green, olive, brown, purple, blue, Sea urchins move slowly, feeding primarily on algae. Sea otters, starfish, wolf eels, triggerfish, and other predators hunt and their roe is a delicacy in many cuisines. The name urchin is an old word for hedgehog, which sea urchins resemble, Sea urchins are members of the phylum Echinodermata, which also includes sea stars, sea cucumbers, brittle stars, and crinoids. Like other echinoderms, they have five-fold symmetry and move by means of hundreds of tiny, transparent, the symmetry is not obvious in the living animal, but is easily visible in the dried test. The irregular sea urchins are an infra-class inside the Euechinoidea, called Irregularia, irregular echinoids include, flattened sand dollars, sea biscuits, and heart urchins. Together with sea cucumbers, they make up the subphylum Echinozoa, Sea cucumbers and the irregular echinoids have secondarily evolved diverse shapes. Urchins typically range in size from 6 to 12 cm, although the largest species can reach up to 36 cm, like other echinoderms, sea urchin early larvae have bilateral symmetry, but they develop five-fold symmetry as they mature. This is most apparent in the sea urchins, which have roughly spherical bodies with five equally sized parts radiating out from their central axes. Several sea urchins, however, including the sand dollars, are oval in shape, with front and rear ends. In these urchins, the surface of the body is slightly domed. This irregular body form has evolved to allow the animals to burrow through sand or other soft materials, Sea urchins tube feet arise from the five ambulacral grooves. Tube feet are moved by a vascular system, which works through hydraulic pressure, allowing the sea urchin to pump water into and out of the tube feet. The lower half of a sea urchins body is referred to as the surface, because it contains the mouth. The internal organs are enclosed in a shell or test composed of fused plates of calcium carbonate covered by a thin dermis and epidermis. The test is rigid, and divides into five ambulacral grooves separated by five interambulacral areas, each of these areas consists of two rows of plates, so the sea urchin test includes 20 rows of plates in total. The plates are covered in rounded tubercles, to which the spines are attached, the inner surface of the test is lined by peritoneum
7.
Human
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Modern humans are the only extant members of Hominina tribe, a branch of the tribe Hominini belonging to the family of great apes. Several of these hominins used fire, occupied much of Eurasia and they began to exhibit evidence of behavioral modernity around 50,000 years ago. In several waves of migration, anatomically modern humans ventured out of Africa, the spread of humans and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide. Humans are uniquely adept at utilizing systems of communication for self-expression and the exchange of ideas. Humans create complex structures composed of many cooperating and competing groups, from families. Social interactions between humans have established a wide variety of values, social norms, and rituals. These human societies subsequently expanded in size, establishing various forms of government, religion, today the global human population is estimated by the United Nations to be near 7.5 billion. In common usage, the word generally refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of hominid and hominin have changed during the recent decades with advances in the discovery, there is also a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species. The English adjective human is a Middle English loanword from Old French humain, ultimately from Latin hūmānus, the words use as a noun dates to the 16th century. The native English term man can refer to the species generally, the species binomial Homo sapiens was coined by Carl Linnaeus in his 18th century work Systema Naturae. The generic name Homo is a learned 18th century derivation from Latin homō man, the species-name sapiens means wise or sapient. Note that the Latin word homo refers to humans of either gender, the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. The closest living relatives of humans are chimpanzees and gorillas, with the sequencing of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. The gibbons and orangutans were the first groups to split from the leading to the humans. The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch, during this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. There is little evidence for the divergence of the gorilla, chimpanzee. Each of these species has been argued to be an ancestor of later hominins
8.
Adult development
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Adult development encompasses the changes that occur in biological, psychological, and interphonal domains of human life from the end of adolescence until the end of ones life. These changes may be gradual or rapid, and can reflect positive, negative, changes occur at the cellular level and are partially explained by biological theories of adult development and aging. Biological changes influence psychological and interpersonal/social developmental changes, which are described by stage theories of human development. Stage theories typically focus on “age-appropriate” developmental tasks to be achieved at each stage, erik Erikson and Carl Jung proposed stage theories of human development that encompass the entire life span, and emphasized the potential for positive change very late in life. The concept of adulthood has legal and socio-cultural definitions, the legal definition of an adult is a person who has reached the age at which they are considered responsible for their own actions, and therefore legally accountable for them. This is referred to as the age of majority, which is age 18 in most cultures and this may or may not coincide with the legal definition. Jeanne Louise Calment exemplifies successful aging as the longest living person and her long life can be attributed to her genetics and her active lifestyle and optimistic attitude. She enjoyed many hobbies and physical activities and believed that laughter contributed to her longevity and she poured olive oil on all of her food and skin, which she believed also contributed to her long life and youthful appearance. Changes in adulthood have been described by a number of theories and metatheories, Life span development is an overarching framework that considers individual development from conception to old age. The framework considers the accumulation of developmental gains and losses. According to this theory, life span development has multiple trajectories and causes, individual variation is a hallmark of this theory – not all individuals develop and age at the same rate and in the same manner. Erik Erikson developed stages of ego development that extended through childhood, adolescence and he was trained in psychoanalysis and was highly influenced by Freud, but unlike Freud, Erikson believed that social interaction is very important to the individuals psychosocial development. His stage theory consists of 8 stages in life from birth to old age, during each stage, one developmental task is dominant, but may be carried forward into later stages as well. According to Erikson, individuals may experience tension when advancing to new stages of development and it offers a standard method of examining the universal pattern of development. The archaic stage is characterized by consciousness, while the monarchic stage represents the beginning of logical. Youth, Maturing sexuality, growing consciousness, and a realization that the days of childhood are gone forever. People strive to gain independence, find a mate, and raise a family, middle Life, The realization that you will not live forever creates tension. If you desperately try to cling to youth, you will fail in the process of self-realization, Jung believed that in midlife, one confronts ones shadow
9.
Fertilisation
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The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation. In 1784, Spallanzani established the need of interaction between the females ovum and males sperm to form a zygote, oscar Hertwig, in Germany, described the fusion of nuclei of spermatozoa and of ova from sea urchin. In flowering plants there are two sperm from each pollen grain, in seed plants, after pollination, a pollen grain germinates, and a pollen tube grows and penetrates the ovule through a tiny pore called a micropyle. The sperm are transferred from the pollen through the pollen tube, bryophyte is a traditional name used to refer to all embryophytes that do not have true vascular tissue and are therefore called non-vascular plants. Some bryophytes do have specialised tissues for the transport of water, however, since these do not contain lignin, a fern is a member of a group of roughly 12,000 species of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular and they have stems and leaves, like other vascular plants. Most ferns have what are called fiddleheads that expand into fronds, the gymnosperms are a group of seed-producing plants that includes conifers, Cycads, Ginkgo, and Gnetales. The term gymnosperm comes from the Greek composite word γυμνόσπερμος, meaning naked seeds and their naked condition stands in contrast to the seeds and ovules of flowering plants, which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, often modified to form cones, the pollen tube does not directly reach the ovary in a straight line. It travels near the skin of the style and curls to the bottom of the ovary, then near the receptacle, it breaks through the ovule through the micropyle, after being fertilised, the ovary starts to swell and develop into the fruit. With multi-seeded fruits, multiple grains of pollen are necessary for syngamy with each ovule, the growth of the pollen tube is controlled by the vegetative cytoplasm. The sperms are interconnected and dimorphic, the one, in a number of plants, is also linked to the tube nucleus and the interconnected sperm. Double fertilisation is the process in angiosperms in which two sperm from each pollen tube fertilise two cells in a gametophyte that is inside an ovule. After the pollen tube enters the gametophyte, the tube nucleus disintegrates. This is the point when fertilisation actually occurs, pollination and fertilisation are two separate processes, the nucleus of the other sperm cell fuses with two haploid polar nuclei in the centre of the gametophyte. This triploid cell divides through mitosis and forms the endosperm, a nutrient-rich tissue, the two central-cell maternal nuclei that contribute to the endosperm arise by mitosis from the single meiotic product that also gave rise to the egg. Therefore, maternal contribution to the constitution of the triploid endosperm is double that of the embryo
10.
Developmental psychology
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Developmental psychology is the scientific study of how and why human beings change over the course of their life. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and this field examines change across three major dimensions, physical development, cognitive development, and socioemotional development. Developmental psychology examines the influences of nature and nurture on the process of human development, many researchers are interested in the interaction between personal characteristics, the individuals behavior and environmental factors, including social context and the built environment. Ongoing debates include biological essentialism vs. neuroplasticity and stages of development vs. dynamic systems of development, influential developmental psychologists from the 20th century include Urie Bronfenbrenner, Erik Erikson, Sigmund Freud, Jean Piaget, Barbara Rogoff, Esther Thelen, and Lev Vygotsky. Watson and Jean-Jacques Rousseau are typically cited as providing the foundations for modern developmental psychology, in the mid-18th century Jean Jacques Rousseau described three stages of development, infants, puer and adolescence in Emile, Or, On Education. Rousseaus ideas were taken up strongly by educators at the time, stanley Hall, who attempted to correlate ages of childhood with previous ages of mankind. James Mark Baldwin who wrote essays on topics that included Imitation, A Chapter in the Natural History of Consciousness and Mental Development in the Child, Baldwin was heavily involved in the theory of developmental psychology. Sigmund Freud, whose concepts were developmental, had a significant impact on public perceptions, Sigmund Freud believed that we all had a conscious, preconscious, and unconscious level. In the conscious we are aware of our mental process, the preconscious involves information that, though not currently in our thoughts, can be brought into consciousness. Lastly, the unconscious includes mental processes we are unaware of and he believed there is tension between the conscious and unconscious, because the conscious tries to hold back what the unconscious tries to express. To explain this he developed three personality structures, the id, ego, and superego, the id, the most primitive of the three, functions according to the pleasure principle, seek pleasure and avoid pain. The superego plays the critical and moralizing role, and the ego is the organized, based on this, he proposed five universal stages of development, that each are characterized by the erogenous zone that is the source of the childs psychosexual energy. The first is the stage, which occurs from birth to 12 months of age. During the oral stage the libido is centered in a babys mouth, the baby is able to suck. The second is the stage, from one to three years of age. During the anal stage, the child defecates from the anus, the third is the phallic stage, which occurs from three to five years of age. During the phallic stage, the child is aware of their sexual organs, the fourth is the latency stage, which occurs from age five until puberty. During the latency stage, the sexual interests are repressed
. PMID 23856356.
