See enzymes in this website

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/enzymes/enzymes1.shtml

Flowering plants for S2

An Introduction to Vegetative Reproduction


Vegetative Reproduction

is a form of asexual reproduction in plants. It does not involve flowers, pollination and seed production. Instead, a new plant grows from a vegetative part, usually a stem, of the parent plant. However, plants which reproduce asexually almost always reproduce sexually as well, bearing flowers, fruits and seeds. Vegetative reproduction from a stem usually involves the buds. Instead of producing a branch, the bud grows into a complete plant which eventually becomes self-supporting. Since no gametes are involved, the plants produced asexually have identical genomes and the offspring form what is known as a clone. In some cases of vegetative reproduction, the structures involved also become storage organs and swell with stored food, e.g. potatoes.

The principal types of vegetative reproduction structures are bulbs, corms, rhizomes and runners.

Bulbs

Bulbs consist of very short stems with closely packed leaves arranged in concentric circles round the stem. These leaves are swollen with stored food e.g. onion. A terminal bud will produce next year’s flowering shoot and the lateral (axillary) buds will produce new plants.


Corms

Corms also have a short stem but in this case it is the stem itself which swells and stores food. The circular leaves form only papery scales. As with bulbs, the terminal bud grows into a flowering shoot and the lateral buds produce new plants.


Rhizomes

Rhizomes are stems which grow horizontally under the ground. In some cases the underground stems are swollen with food reserves e.g. iris. The terminal bud turns upwards to produce the flowering shoot and the lateral buds may grow out to form new rhizomes.


Runners

Runners are also horizontal stems growing from the parent plant, but they grow above ground. When their terminal buds touch the ground they take root and produce new plants.


Advantages of vegetative reproduction

Since food stores are available throughout the year and the parent plant with its root system can absorb water from quite a wide area, two of the hazards of seed germination are reduced. Buds are produced in an environment where the parent is able to flourish, but many seeds dispersed from plants never reach a suitable situation for effective germination.

Vegetative reproduction does not usually result in rapid and widespread distribution of offspring in the same way as seed dispersal, but tends to produce a dense clump of plants with little room for competitors between them. Such groups of plants are very persistent and, because of their buds and underground food stores, can still grow after their foliage has been destroyed by insects, fire, or cultivation. Those of them regarded as weeds are difficult to eradicate, since even a small piece of rhizome bearing a bud can give rise to a new colony (clone).

Bulbs - Snowdrop

In the snowdrop and daffodil, the bulb is formed by the leaf bases which completely encircle the short, conical stem. The part of the leaf above ground makes food by photosynthesis and sends it to the leaf bases which swell as they store the food. In the following year the stored food is used for the early growth of the bulb.

Life cycle of Daffodil
In the spring, adventitious roots grow out of the stem, and the leaves begins to grow above ground, making use of the stored food in the fleshy leaf bases which consequently shrivel. During late spring some of the food made in the leaves in the daffodil is sent to the leaf bases which swell and form a new bulb inside the old one.

Life cycle of Tulip and Onion
In these bulbs, the food is not sent to the leaf bases but to the lateral buds. As these buds enlarge they form two or more ‘daughter’ bulbs inside the old bulb. The leaves of the old bulb shrivel and dry out forming the dry scales which surround the daughter bulbs. In both cases, when the daughter bulbs grow, they form a clump, together with the parent bulb.

Corms - Crocus
Plants with bulbs store food in special leaves or leaf bases. Plants with corms store food in the stem, which is very short and swollen. When the foliage has died off, the leaf bases, where they encircle the short stem, form protective scaly coverings. A familiar corms is that of the crocus, and the wild arum corm is illustrated on p.1. Since the corm is a stem, it has lateral buds which can grow into new plants. The stem remains below ground all its life, only the leaves and flower stalk coming above ground.

Life Cycle of Corm
In Spring, the food stored in the corm enables the terminal bud to grow rapidly and produce leaves and flowers above ground. Later in the year, food made by the leaves is sent back, not to the old corm, but to the base of the stem immediately above it. This region swells and forms a new corm on top of the old, now shrivelled, corm. Some of the lateral buds on the old corm have also grown and produced new plants with corms.

Contractile Roots
The formation of one corm on top of another tends to bring the successive corms nearer and nearer to the soil surface. Adventitious roots develop from the base of the new corm. Once these have grown firmly into the soil, a region near their junction with the stem contracts and pulls the new corm down, keeping it at a constant level in the soil. Wrinkles can be seen on these contractile roots where shrinkage has taken place. Bulbs also have contractile roots which counteract the tendency in successive generations to grow out of the soil.

Rhizomes

In plants with rhizomes, the stem remains below ground but continues to grow horizontally. The old part of the stem does not die away as in bulbs and corms, but lasts for several years. In the iris, the terminal bud turns up and produces leaves and flowers above ground. The old leaf bases form circular scales round the rhizome, which is swollen with food reserves. Lateral buds grow into new rhizomes.

Life Cycle of Rhizome
The annual cycle of a rhizome is similar to that of a corm. In late spring/early summer, food from the leaves passes back to the rhizome, and a lateral bud uses it, grows horizontally underground, and so continues the rhizome. Other lateral buds produce new rhizomes which branch from the parent stem. The terminal buds of these branches curve upwards and produce new leafy shoots and flowers. Contractile, adventitious roots grow from the nodes of the underground stem and keep it at a constant depth.

Runners
Plants such as the strawberry have a very short stem, called a rootstock, with thin scale leaves,. Foliage leaves and flowers grow from the buds in the axils of the scale leaves. Some of the lower buds produce shoots which grow horizontally over the surface of the ground and bear scale leaves and buds. The terminal buds of these runners turn up and produce daughter plants some distance away from the parent, the new plants developing adventitious roots. Later, the runner shrivels away. The runner does not store food but conducts it from the parent plant to the daughters, until they are well developed.

Stem tubers - potato
In the potato plant, lateral buds at the base of the stem produce shoots which grow laterally at first and then down into the ground. These are comparable to rhizomes, as they are underground stems with tiny scale leaves and lateral buds. They do not swell evenly along their length with stored food.

Annual cycle - potato
Food made in the leaves passes to the ends of these rhizomes, which swell and form the tubers we call potatoes. Since the potato tuber is a stem, it has leaves and lateral buds; these are the familiar ‘eyes’. Each one of these can produce a new shoot in the following year, using the food stored in the tuber. The old tubers shrivel and rot away at the end of the season

Stolons
Blackberry stems form a rather different type of runner in which the main shoot forms the new individual. When the growing end of a shoot arches over and touches the ground, the terminal bud curves up, producing a new shoot which soon develops adventitious roots.

Grafting
A bud or shoot from one plant is inserted into a cleft or under the bark on the stem of a closely related variety. The rooted portion is called the stock; the bud or shoot being grafted is the scion. The stock is obtained by growing a plant from seed then cutting away the shoot. The scion is a branch or a bud cut from a cultivated variety with the required characteristics of flower colour, fruit quality, etc.

Rose plants grown from seed would produce a wide variety of plants, only a few of which would retain all the desirable features of the parent plant. Most of them would be like wild roses. Similarly, most of the apple trees grown from seed would bear only small, sour ‘crab-apples'. By taking cuttings and making grafts, the inbred characteristics of the plant are preserved and you can guarantee that all the new individuals produced by this kind of artificial propagation will be the same.

Cuttings
It is possible to produce new individuals from certain plants by putting the cut end of a shoot into water or moist earth. Roots grow from the base of the stem into the soil while the shoot continues to grow and produce leaves.

In some cases the cut end of the stem may be treated with a rooting 'hormone' to promote root growth. Evaporation from the shoot is reduced by covering it with polythene or a glass jar. Carnations, geraniums and chrysanthemums are commonly propagated from cuttings.

Tissue culture
Once a cell has become part of a tissue it usually loses the ability to reproduce. However, the nucleus of any plant cell still holds all the 'instructions' (genes) for making a complete plant and in certain circumstances they can be brought back into action. In laboratory conditions single plant cells can be induced to divide and grow into complete plants. One technique is to take a small piece of plant tissue from a root or stem and treat it with enzymes to separate it into individual cells The cells are then provided with particular plant 'hormones’ which induce cell division and, eventually the formation of roots, stems and leaves.

An alternative method is to start with a small piece of tissue and place it on a nutrient jelly (agar). Cells in the tissue start to divide and produce many cells forming a shapeless mass called a callus. If the callus is then provided with the appropriate ‘hormones’ it develops into a complete plant.

S3 Genetics Game

http://www.what2learn.com/games/play/12505/

Definition,puberty, Psychology, Sexuality

Adolescence (from the Latin: adolescere meaning "to grow up") is a transitional stage of physical and mental human development that occurs between childhood and adulthood. This transition involves biological (i.e. pubertal), social, and psychological changes, though the biological or physiological ones are the easiest to measure objectively. Historically, puberty has been heavily associated with teenagers and the onset of adolescent development.[1][2] In recent years, however, the start of puberty has had somewhat of an increase in preadolescence (particularly females, as seen with early and precocious puberty); adolescence has had an occasional extension beyond the teenage years (typically males). These changes have made it more difficult to rigidly define the time frame in which adolescence occurs.[3][4][5]

The end of adolescence and the beginning of adulthood varies by country and by function, and furthermore even within a single nation-state or culture there can be different ages at which an individual is considered to be (chronologically and legally) mature enough to be entrusted by society with certain tasks. Such milestones include, but are not limited to, driving a vehicle, having legal sexual relations, serving in the armed forces or on a jury, purchasing and drinking alcohol, voting, entering into contracts, completing certain levels of education, and marrying.

Adolescence is usually accompanied by an increased independence allowed by the parents or legal guardians and less supervision, contrary to the preadolescence stage.

Puberty

Upper body of teenage boy. The structure has changed to resemble an adult form.Main article: Puberty
Puberty is a period of several years in which rapid physical growth and psychological changes occur, culminating in sexual maturity. The average onset of puberty is at 10 for girls and age 12 for boys.[6] Every person's individual timetable for puberty is influenced primarily by heredity, although environmental factors, such as diet and exercise, also exert some influence.[6][7][8] These factors can also contribute to delayed puberty.

Puberty begins with a surge in hormone production, which in turn, causes a number of physical changes.[6] It is also the stage of life in which a child develops secondary sex characteristics (for example, a deeper voice and larger adam's apple in boys, and development of breasts and more curved and prominent hips in girls) as his or her hormonal balance shifts strongly towards an adult state. This is triggered by the pituitary gland, which secretes a surge of hormonal agents into the blood stream, initiating a chain reaction. The male and female gonads are subsequently activated, which puts them into a state of rapid growth and development; the triggered gonads now commence the mass production of the necessary chemicals. The testes primarily release testosterone, and the ovaries predominantly dispense estrogen. The production of these hormones increases gradually until sexual maturation is met. Some boys may develop gynecomastia due to an imbalance of sex hormones, tissue responsiveness or obesity.[9][10] Put simply, puberty is the time when a child's body starts changing into an adult's body.[6]

Facial hair in males normally appears in a specific order during puberty: The first facial hair to appear tends to grow at the corners of the upper lip, typically between 14 to 16 years of age.[11][12] It then spreads to form a moustache over the entire upper lip. This is followed by the appearance of hair on the upper part of the cheeks, and the area under the lower lip.[11] The hair eventually spreads to the sides and lower border of the chin, and the rest of the lower face to form a full beard.[11] As with most human biological processes, this specific order may vary among some individuals. Facial hair is often present in late adolescence, around ages 17 and 18, but may not appear until significantly later.[12][13] Some men do not develop full facial hair for 10 years after puberty.[12] Facial hair will continue to get coarser, darker and thicker for another 2–4 years after puberty.[12]

The major landmark of puberty for males is the first ejaculation, which occurs, on average, at age 13.[14] For females, it is menarche, the onset of menstruation, which occurs, on average, between ages 12 and 13.[7] The age of menarche is influenced by heredity, but a girl's diet and lifestyle contribute as well.[7] Regardless of genes, a girl must have certain proportion of body fat to attain menarche.[7] Consequently, girls who have a high-fat diet and who are not physically active begin menstruating earlier, on average, than girls whose diet contains less fat and whose activities involve fat reducing exercise (e.g. ballet and gymnastics).[7][8] Girls who experience malnutrition or are in societies in which children are expected to perform physical labor also begin menstruating at later ages.[7]

The timing of puberty can have important psychological and social consequences. Early maturing boys are usually taller and stronger than their friends.[15] They have the advantage in capturing the attention of potential partners and in becoming hand-picked for sports. Pubescent boys often tend to have a good body image, are more confident, secure, and more independent.[16] Late maturing boys can be less confident because of poor body image when comparing themselves to already developed friends and peers. However, early puberty is not always positive for boys; early sexual maturation in boys can be accompanied by increased aggressiveness due to the surge of hormones that affect them.[16] Because they appear older than their peers, pubescent boys may face increased social pressure to conform to adult norms; society may view them as more emotionally advanced, despite the fact that their cognitive and social development may lag behind their appearance.[16] Studies have shown that early maturing boys are more likely to be sexually active and are more likely to participate in risky behaviors.[17]

For girls, early maturation can sometimes lead to increased self-consciousness, though a typical aspect in maturing females.[18] Because of their bodies developing in advance, pubescent girls can become more insecure.[18] Consequently, girls that reach sexual maturation early are more likely than their peers to develop eating disorders. Nearly half of all American high school girls' diet is to lose weight.[18] In addition, girls may have to deal with sexual advances from older boys before they are emotionally and mentally mature.[19] In addition to having earlier sexual experiences and more unwanted pregnancies than late maturing girls, early maturing girls are more exposed to alcohol and drug abuse.[20] Those who have had such experiences tend to perform less well in school than their "inexperienced" age peers.[21]

By ages 15-17, girls have usually reached full physical development.[18][22] By age 16, boys are close to completing puberty,[18] which is usually achieved by ages 17 or 18.[22] Teenage and early adult males may continue to gain natural muscle growth even after puberty.[16]
Psychology
Main article: Adolescent psychology
Adolescent psychology is associated with notable changes in mood sometimes known as mood swings. Cognitive, emotional and attitudinal changes which are characteristic of adolescence, often take place during this period, and this can be a cause of conflict on one hand and positive personality development on the other.

Because the adolescents are experiencing various strong cognitive and physical changes, for the first time in their lives they may start to view their friends, their peer group, as more important and influential than their parents/guardians. Because of peer pressure, they may sometimes indulge in activities not deemed socially acceptable, although this may be more of a social phenomenon than a psychological one.[23] This overlap is addressed within the study of psychosociology.

The home is an important aspect of adolescent psychology: home environment and family have a substantial impact on the developing minds of teenagers, and these developments may reach a climax during adolescence. For example, abusive parents may lead a child to "poke fun" at other classmates when he/she is seven years old or so, but during adolescence it may become progressively worse. If the concepts and theory behind right or wrong were not established early on in a child's life, the lack of this knowledge may impair a teenager's ability to make beneficial decisions as well as allowing his/her impulses to control his/her decisions.

In the search for a unique social identity for themselves, adolescents are frequently confused about what is 'right' and what is 'wrong.' G. Stanley Hall denoted this period as one of "Storm and Stress" and, according to him, conflict at this developmental stage is normal and not unusual. Margaret Mead, on the other hand, attributed the behavior of adolescents to their culture and upbringing.[24] However, Piaget, attributed this stage in development with greatly increased cognitive abilities; at this stage of life the individual's thoughts start taking more of an abstract form and the egocentric thoughts decrease, hence the individual is able to think and reason in a wider perspective.[25]

Positive psychology is sometimes brought up when addressing adolescent psychology as well. This approach towards adolescents refers to providing them with motivation to become socially acceptable and notable individuals, since many adolescents find themselves bored, indecisive and/or unmotivated.[26]

Adolescents may be subject to peer pressure within their adolescent time span, consisting of the need to have sex, consume alcoholic beverages, use drugs, defy their parental figures, or commit any activity in which the person who is subjected to may not deem appropriate, among other things. Peer pressure is a common experience between adolescents and may result briefly or on a larger scale. If it results on a larger scale, the adolescent needs medical advice or treatment.[27]

It should also be noted that adolescence is the stage of a psychological breakthrough in a person's life when the cognitive development is rapid[28] and the thoughts, ideas and concepts developed at this period of life greatly influence one's future life, playing a major role in character and personality formation.[29]

Struggles with adolescent identity and depression usually set in when an adolescent experiences a loss. The most important loss in their lives is the changing relationship between the adolescent and their parents. Adolescents may also experience strife in their relationships with friends. This may be due to the activities their friends take part in, such as smoking, which causes adolescents to feel as though participating in such activities themselves is likely essential to maintaining these friendships. Teen depression can be extremely intense at times because of physical and hormonal changes but emotional instability is part of adolescence. Their changing mind, body and relationships often present themselves as stressful and that change, they assume, is something to be feared.[30]

Views of family relationships during adolescence are changing. The old view of family relationships during adolescence put an emphasis on conflict and disengagement and thought storm and stress was normal and even inevitable. However, the new view puts emphasis on transformation or relationships and maintenance of connectedness.

[edit] Sexuality
Main article: Adolescent sexuality
Adolescent sexuality refers to sexual feelings, behavior and development in adolescents and is a stage of human sexuality. Sexuality and sexual desire usually begins to intensify along with the onset of puberty. The expression of sexual desire among adolescents (or anyone, for that matter), might be influenced by family values and the culture and religion they have grown up in (or as a backlash to such), social engineering, social control, taboos, and other kinds of social mores.


Teenage couples at a fair in the American West.In contemporary society, adolescents also face some risks as their sexuality begins to transform. Whilst some of these such as emotional distress (fear of abuse or exploitation) and sexually transmitted diseases (including HIV/AIDS) may not necessarily be inherent to adolescence, others such as pregnancy (through failure or non-use of contraceptives) are seen as social problems in most western societies. In terms of sexual identity, all sexual orientations found in adults are also represented among adolescents.

According to anthropologist Margaret Mead and psychologist Albert Bandura, the turmoil found in adolescence in Western society has a cultural rather than a physical cause; they reported that societies where young women engaged in free sexual activity had no such adolescent turmoil.

In a 2008 study conducted by YouGov for Channel 4, 20% of 14−17-year-olds surveyed revealed that they had their first sexual experience at 13 or under.[31]

The age of consent to sexual activity varies widely between international jurisdictions, ranging from 12 to 21 years.[32]

poli 2 Transport in plants

See this adress for more information http://www.jochemnet.de/fiu/BSC1011/BSC1011_9/index.htm

Classification!!

Classification of Organisms

Organismal diversity is the product of evolution. Evolutionary paths are branched and numerous, though most arrive at dead ends with organisms which do not survive in the face of environmental change. In this lecture we consider these evolutionary paths (called lineages), ignoring for the moment the processes that carry organisms along them.
While the lineage of any given organism may have twisted repeatedly according to the whims of chance and change, key nodes may nevertheless be tracked retrospectively. These nodes consist of times of identifiable change, particularly points of divergence between two lineages (speciation events). The delineation of these nodes in organismal lineages is accomplished through fossil reconstruction of the past as well as by comparing extant organisms, looking for similarities and differences in anatomies, physiologies, genes, behaviors, etc. From this information classification and phylogenetic reconstruction is accomplished. Classification according to similarity:
Carolus Linnaeus developed a system of classification of every (then) known organism.
This system is based on creating and differentiating groups in terms of structural (and other) similarities and differences.
Linnaeus also invented binomial nomenclature to keep track of group members.
Systematics
Systematics is the study of the diversity of organisms and their evolutionary relationships.
Science of classification:
Systematics is the science of the classification of organisms.
The main goal of systematics is the discovery and codification of phylogenetic relationships between organisms.
"The term systematics often is used for taxonomy. However, many taxonomists define it in more general terms as 'the scientific study of organisms with the ultimate object of characterizing and arranging them in an orderly manner.' Any study of the nature of organisms, when the knowledge gained is used in taxonomy, is a part of systematics. Thus (systematics) encompasses disciplines such as morphology, ecology, epidemiology, biochemistry, molecular biology, and physiology." (p. 391, Prescott et al., 1996)
Taxon [sing., taxa, pl.]
A taxon is a phylogenetic grouping of organisms.
Taxonomy
Identification and classification:
Taxonomy is the science concerned with the:
identification
classification
nomenclature
of organisms.
"Taxonomy [Greek taxis, arrangement or order, and nomos, law, or nemein, to distribute or govern] is defined as the science of biological classification. In a broader sense it consists of three separate but interrelated parts: classification, nomenclature, and identification." (p. 391, Prescott et al., 1996)
Note that the terms systematics and taxonomy can often be used semantically in a nearly indistinguishable manner.
Identification
Identification is "the practical side of taxonomy, the process of determining that a particular (organism) belongs to a recognized taxon." (p. 391, Prescott et al., 1996)
Classification
Classification is "the arrangement of organisms into groups or taxa." (p. 391, Prescott et al., 1996)
Nomenclature
Name assignment:
Nomenclature is "the branch of taxonomy concerned with the assignment of names to taxonomic groups in agreement with published rules." (p. 391, Prescott et al., 1996)
Note that ideally names have taxonimic meaning, i.e., they give clues to phylogenetic relationships.
Hierarchical classification
Hierarchy of designations:
The full description of a given organism's place among all the world's organisms does not end with its binomial designation.
There exists a hierarchy of designations only the last of which describe genera and species denomination.
"A category in any rank unites groups in the level below it based on shared properties." (p. 391, Prescott et al., 1996)
The major designations, listed in terms of increasing specificity, include:
domain (empire/super-kingdom)
kingdom
phylum
class
order
family
genus
species

Various mnemonics exist to help you remember these designations from kingdom through species
Did King Peter Came Over From Geneva Switzerland?

Dichotomus key Senior 1

Activity
Create a dichotomous key using the following list of specimens: pine tree, clam, rock,
robin, tin can, deer, oak tree, mouse, dandelion, Paramecium, bicycle, ant
Here's an example in written form using these items:
1. a. Organism is living........................................................go to 4.
1. b. Organism is nonliving..................................................go to 2.
2. a. Object is metallic........................................................go to 3.
2. b. Object is nonmetallic..................................................ROCK.
3. a. Object has wheels......................................................BICYCLE.
3. b. Object does not have wheels......................................TIN CAN.
4. a. Organism is microscopic...................................PARAMECIUM.
4. b. Organism is macroscopic............................................go to 5.
5. a. Organism is a plant.....................................................go to 6.
5. b. Organism is an animal.................................................go to 8.
6. a. Plant has a woody stem..............................................go to 7.
6. b. Plant has a herbaceous stem.................................DANDELION.
7. a. Tree has needle like leaves.....................................PINE TREE.
7. b. Tree has broad leaves............................................OAK TREE.
8. a. Organism lives on land................................................go to 9.
8. b. Organism lives in water...............................................CLAM.
9. a. Organism has 4 legs or fewer......................................go to 10.
9. b. Organism has more than 4 legs...................................ANT.
10 a. Organism has fur........................................................go to 11.
10 b. Organism has feathers................................................ROBIN.
11 a. Organism has hooves.................................................DEER.
11 b. Organism has no hooves............................................MOUSE.