Higher Biology Revision Exercise Unit 3 Control and

Higher Biology Revision Exercise Unit 3 Control and Regulation

Plant Growth/Growth Patterns 1. Growth is the ______ irreversible increase in the mass of an organism 2. In plants growth is restricted to regions called _____. meristems 3. ____ Primary plant growth occurs at ______ apical meristems (root and shoot tips) where newly formed cells become elongated, differentiated vacuolated and ______. 4. _____ Secondary growth occurs in a perennial plant at a _______ lateral cambium meristem called _____.

rings of secondary xylem 5. Cambial activity produces annual ______ and phloem. Each ring of secondary ______ xylem contains a region of large vessels called _______ spring wood and a region of smaller vessels called ____ autumn wood. 6. ____ Animals do not possess meristems. Instead growth occurs all body over a developing animal’s _____. 7. _____ Flowering plants (angiosperms) have extensive powers of regeneration whereas mammals have only _______ limited powers. _______ 8. Investigations into growth often involve measuring a variable height length etc. factor such as fresh weight, _______,

9. A graph of the results normally takes the form of a ____ sigmoid (S -shaped) growth curve. 10. Growth ____ patterns vary from one type of organism to another.

Genetic Control 1. The characteristic features of a cell are controlled by its______. genes 2. To prevent _____ resources being wasted, some genes can be switched on and off as required. 3. The operon (_______) Jacob-Monod hypothesis states that a operator gene is structural gene remains switched off while its ____ repressor from a regulator gene. The combined with a _____ structural gene becomes switched on and codes for its protein inducer prevents the repressor combining with the when an ____ operator gene.

4. All the chemical processes that occur in a living organism are metabolism known collectively as its ______. 5. Each stage in a metabolic _____ pathway is controlled by an enzyme. 6. Production of each ____ enzyme is controlled by a particular gene (or group of genes). 7. A ____ mutated gene is unable to code the information needed to produce its enzyme. Lack of this enzyme may lead to an inborn error PKU _____ of metabolism such as _____. 8. During ______, differentiation cells become specialised to perform functions specific _____.

9. Within a differentiated cell, only certain genes continue to operate and the other genes are switched _____. off ____ 10. In some cases genes that were switched off can be switched on reversal of differentiation. ___ again bringing about a ____ 11. Two categories of genes exist: the genes that code for vital metabolites (and are switched on in all cells); the genes that ______ proteins characteristic of a particular type of cell ( and code for ____ cell are switched on only in that type of _____.

Hormonal influences on growth 1. The pituitary gland produces both _______ growth hormone (which thyroid stimulating hormone promotes human growth) and ____________ (TSH). 2. The ______ thyroid gland responds to TSH by producing ____ thyroxine which controls metabolic processes. 3. The auxins make up a group of plant growth substances auxin is called indole acetic acid (hormones). The most common ______ (____). IAA

4. IAA is produced in root and shoot tips and promotes cell division cell _____ elongation and differentiation of cells. ____, 5. Low concentrations of auxin which stimulate ____ root elongation Higher concentrations of auxin which have little effect on shoots. ______ inhibit root elongation. stimulate shoot elongation ______ 6. Unequal distribution of auxin causes shoots to _____ bend phototropic movements. producing _____ 7. Apical buds exert apical _____ dominance by producing high lateral buds. concentrations of auxin which inhibit growth of ______

8. Auxin prevents leaf and fruit _____ abscission and promotes fruit formation. 9. Synthetic auxins act as _____ herbicides by disrupting growth of weeds more than grass-like plants which absorb broad-leaved ______ narrow leaves. less through their ______ 10. Synthetic auxins stimulate formation of _____ adventitious roots on stem cuttings. 11. The _____ gibberellins make up a second group of plant growth substances. The most common gibberellin is called gibberellic acid (GA). _______

12. GA promotes cell division and elongation in _______. stems 13. GA reverses genetic ____ dwarfism by promoting stem ____ internode elongation. 14. GA induces production of _____ a-amylase in cereal grains and dormancy in winter buds. breaks ____

Physiological Homeostasis 1. Nitrogen, _____, phosphorus potassium and _____ magnesium are four macro-elements needed by plants for healthy growth. 2. A plant grown in a water culture experiment lacking one essential macro-element displays certain deficiency ____ symptoms. 3. _____ Lead inhibits the action of certain enzymes, It is poisonous to intelligence of humans and may have a detrimental effect on the _____ children. 4. Iron is essential to humans for the formation of ______. haemoglobin

5. ____ Calcium is essential to humans for the formation of healthy teeth bones and _____. 6. _____ Vitamin D is needed to promote the uptake of calcium ions by rickets bone and prevent ______. 7. Drugs such as _______, nicotine alcohol and _____ thalidomide harm a foetus developing human ______. 8. A plant grown in darkness develops a weak ____ long stem and etiolated small curled leaves and is said to be ____.

9. Green plants show positive ______ phototropism by growing light from one direction. towards a source of _____ 10. In order to flower, long day plants require a number of hours of above a critical level. Short day plants need a critical light ______ darkness Such a response by an organism to number of hours of ____. photoperiodism a photoperiod of a certain length is called _______. 11. Seasonal gonadal activity in many birds and mammals is photoperiods of a certain length. stimulated by the arrival of daily ______

12. Small mammals with short gestation periods tend to be ____ long day breeders. Large mammals with long gestation periods tend to short day breeders. be _____ 13. Breeding is timed so that the young are born in ______ spring when the conditions are favourable.

Homeostasis/Populations/Succession 1. To function efficiently, many aspects of the human body’s internal limits ______ environment must be maintained within tolerable _____. 2. Physiological ______ homeostasis is the name given to this maintenance of the internal environment despite changes in the external _______ environment. 3. Homeostasis operates on the principle of ____ negative feedback control. By this means a change in the internal environment is receptors which send messages to ____. effectors detected by _____ These trigger responses which negate the deviation from the norm set point and return the internal environment to its _____.

4. Population ____ dynamics is the study of population changes and the factors which cause them. 5. A population increases until it reaches the _______ carrying capacity of stable the environment and then it remains relatively ______. 6. A _____ population is prevented from increasing in size indefinitely by resistance several factors known collectively as environmental _____. 7. Some of these factors affect the growth of the population in a independent of population density. Other factors operate manner ______ density-dependent manner. in a ________

8. In a natural ecosystem, a population is kept relatively stable by feedback control density-dependent factors effecting negative _____ (homeostasis). 9. The population numbers of many wild plants and animals are monitored by humans. _____ 10. This provides data which helps humans to manage species food to control ____ pest species, to assess pollution levels used for _____, indicator species and to protect and ______ conserve using ____ endangered species.

11. The change which involves a regular progression from a pioneer community of plants to a climax community is called _______ succession _____. 12. During succession each community enjoys a period of shortmodifies the habitat. In doing term stability during which time it ____ favourable to itself and more so it makes the habitat less _____ favourable to its seccessor. 13. The ______ climax community is the final product of succession climatic factors. It enjoys whose nature is determined by soil and _______ replaced by another community. stability and is not ____

14. Compared with a pioneer community, a climax community biomass possesses a more diverse range of species, a higher ____ webs and a more complex set of food _____.