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Do individual mammal hairs absorb water?

Do individual mammal hairs absorb water?


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In my look into the world of shaving I've seen claims that it is better to shave after a shower because the hairs will absorb water and soften, making the shave easier. Likewise, I've seen it claimed that natural hair brushes (i.e. boar and badger hair brushes) should be soaked before use. My question is: do the hair fibers actually absorb water, presumably thickening in the process, or does the water just adsorb onto the surface (maybe lifting the scales in the cuticle) meaning you can wet hair in aggregate, but it doesn't soften when soaked? Especially, is there a side-by-side comparison of a single hair under a microscope before and after soaking showing what happens?


Researching this answer took me to some strange literature, but it appears to suggest a little bit of both (at least for human hair, which is porous, implying that some water can suffuse through the cuticle into the cortex). For example this paper looks at the impact of this effect on drug testing.

There's also a few papers in cosmetics science journals describing various elements and effects of increased hair porosity, but I was unable to find one primary citation which characterised the trait.


Adaptations to polar life in mammals and birds

This Review presents a broad overview of adaptations of truly Arctic and Antarctic mammals and birds to the challenges of polar life. The polar environment may be characterized by grisly cold, scarcity of food and darkness in winter, and lush conditions and continuous light in summer. Resident animals cope with these changes by behavioural, physical and physiological means. These include responses aimed at reducing exposure, such as ‘balling up’, huddling and shelter building seasonal changes in insulation by fur, plumage and blubber and circulatory adjustments aimed at preservation of core temperature, to which end the periphery and extremities are cooled to increase insulation. Newborn altricial animals have profound tolerance to hypothermia, but depend on parental care for warmth, whereas precocial mammals are well insulated and respond to cold with non-shivering thermogenesis in brown adipose tissue, and precocial birds shiver to produce heat. Most polar animals prepare themselves for shortness of food during winter by the deposition of large amounts of fat in times of plenty during autumn. These deposits are governed by a sliding set-point for body fatness throughout winter so that they last until the sun reappears in spring. Polar animals are, like most others, primarily active during the light part of the day, but when the sun never sets in summer and darkness prevails during winter, high-latitude animals become intermittently active around the clock, allowing opportunistic feeding at all times. The importance of understanding the needs of the individuals of a species to understand the responses of populations in times of climate change is emphasized.


ICSE Biology 2021 Specimen Paper for Class-10

based on Further reduced syllabus

  • Answers to this Paper must be written on the paper provided separately.
  • You will not be allowed to write during the first 15 minutes.
  • This time is to be spent in reading the Question Paper.
  • The time given at the head of this paper is the time allowed for writing the answers.
  • Attempt all questions from Section I and any four questions from Section II.
  • The intended marks for questions or parts of questions are given in brackets [ ]

Section -1 (40 Marks)
(Attempt All questions from this section)

Question 1.
(a) Name the following : [5]
(i) The process by which root hairs absorb water from the soil.
(ii) The organ which produces urea.
(iii) The kind of lens required to correct Myopia.
(iv) The pituitary hormone which stimulates contraction of uterus during child birth.
(v) Openings on the stem through which transpiration occurs

(b) Choose the correct answer from the four options given below : [5]
(i) A plant cell may burst when :
(A) Turgor pressure equalises wall pressure.
(B) Turgor pressure exceeds wall pressure.
(C) Wall pressure exceeds turgor pressure.
(D) None of the above
(ii) The individual flattened stacks of membranous structures inside the chloroplasts are known as :
(A) Grana (B) Stroma (C) Thylakoids (D) Cristae
(iii) The nephrons discharge their urine at the :
(A) Urinary bladder (B) Urethra (C) Renal pelvis (D) Renal pyramid
(iv) Gigantism and Acromegaly are due to :
(A) Hyposecretion of Thyroxine
(B) Hyposecretion of Growth hormone
(C) Hypersecretion of Thyroxine
(D) Hypersecretion of Growth hormone
(v) The mineral ion needed for the formation of blood clot is :
(A) Potassium (B) Sodium (C) Calcium (D) Iron

(c) Complete the following paragraph by filling in the blanks (i) to (v) with appropriate words: [5]
To test a leaf for starch, the leaf is boiled in water to (i)________. It is then boiled in Methylated spirit to (ii) ________.The leaf is dipped in warm water to soften it. It is placed in a petri dish, and (iii) ___________. solution is added. The region of the leaf which contains starch, turns (iv) _________. and the region which does not contain starch, turns (v) _________.

(d) Mention the exact location of the following structures :
(i) Thylakoids (ii) Organ of Corti (iii) Lenticels (iv) Bicuspid Value (v) Loop of Henle [5]

Given below is a diagram depicting a defect of the human eye, study the same and then answer the questions that follow : [5]

(i) Name the defect shown in the diagram.
(ii) What are the two possible reasons that cause this defect ?
(iii) Name the type of lens used to correct this defect.
(iv) With the help of a diagram show how the defect shown above is rectified using a suitable lens.

State the main function of the following: [5]

(i) Lymphocytes of blood
(ii) Leydig cells
(iii) Guard cells
(iv) Eustachian tube
(v) Corpus luteum

Match the items given in Column A with the most appropriate ones in Column B and REWRITE the correct matching pairs :
Column A
Column B

(i) Cranial nerves Testosterone
(ii) Leydig cells Natural reflex
(iii) Acetylcholine 12 pairs
(iv) Spinal nerves Prolactin
(v) Sneezing Neurotransmitter
– 18 pairs

– 31 pairs
– Conditioned reflex

Choose the ODD one out from the following terms given and name the CATEGORY to which the others belong: [5]
Example: Nose, Tongue, Arm, Eye
Answer: Odd Term – Arm, Category – Sense organs.
(i) motor nerve, sensory nerve , effector, receptor , stimuli, uriniferous
(ii) Lumen, muscular tissue, connective tissue, pericardium
(iii) Dendrites, Medullary Sheath, Axon, Spinal cord
(iv) Centrosome, Cell wall, Cell membrane, Large vacuoles
(v) Prostate gland, Cowper’s gland, seminal vesicle, seminiferous tubules.

Section – II (40 Marks)

ICSE Biology 2021 Specimen

(Attempt any four questions from this section

Question 2.
(a) The diagram given below represents a stage during cell division. Study the same and answer the questions that follow :

(i) Identify whether it is a plant cell or an animal cell. Give a reasop in support of your answer.
(ii) Name the stage depicted in the diagram.
What is the unique feature observed in this stage?
(iii) Name the type of cell division that occurs during :

(iv) What is the stage that comes before the stage shown in the diagram ?
(v) Draw a neat, labelled diagram of the stage mentioned in (iv) above keeping the chromosome number constant.

(b) The diagram below represents the simplified pathway of the circulation of blood. Study the same and answer the questions that follow :
(i) Name the blood vessels labelled 1 and 2.
(ii) State the function of blood vessels labelled 5 and 8.
(iii) What is the importance of the blood vessel labelled 6 ?
(iv) Which blood vessel will contain a high amount of glucose and amino acids after a meal ?
(v) Draw a diagram of the different blood cells as seen in a smear of human blood. [5]

(a) Differentiate between the following pairs on the basis of what is mentioned in brackets :
(i) Photolysis and Photophosphorylation. (Definition)
(ii) Bicuspid valve and Tricuspid valve. (Function).
(iii)
(iv) Cerebrum and Spinal cord. (Arrangement of nerve cells)
(v) Bowman’s capsule and Malpighian capsule. (Parts included)

(b) Briefly explain the following terms :
(
i) Genes.
(ii) Cytokinesis in plant cells.
(iii) Guttation.
(iv) Diabetes insipidus.

Question-4 (ICSE Biology 2021 Specimen)

(a) An apparatus as shown alongside was set up to investigate a physiolo¬gical process in plants. The setup was w kept in sunlight for two hours. Droplets of water were then seen inside the bell jar. Answer the questions that follow :
(i) Name the process being studied.
(ii) Explain the process named above m Q. 3. (a) (i).
(iii) Why was the pot covered with a plastic sheet ?
(iv) Suggest a suitable control for this experiment.
(v) Mention two ways by, which this process is beneficial to plants.
(vi) List three adaptations in plants to reduce the above mentioned process. [5]

(b) Given below is the outline of the human body showing the important glands : [5]
(i) Name the glands marked 1 to 4.
(ii) Name the hormone secreted by part 2. Give one important function of this hormone.
(iii) Name the endocrine part of the part numbered 3.
(iv) Why is the part labelled 1 called, the master gland ? Which part of the forebrain controls the gland labelled 1 ?
(v) Name the gland, that secretes the ’emergency hormone’.

(a) The diagram given below represents an organ system in the human body. Study the same and answer the questions that follow : [5]

(i) Identify the system.
(ii) Label the parts marked 2 and 4. Mention the function of part 5.
(iii) Name the structural and functional units of the part marked 1.
(iv) What is the fluid that accumulates in part 3? Which is the main nitrogenous waste present in it?
(v) Draw a neat, labelled diagram showing the longitudinal section of part 1.

State whether the following statements are true (T) or false (F).

(a) The main component of the white matter of the brain is perikaryon. (T/F)

(c) A double chain of ganglia, one on each side of the nerve cord belongs to the spinal cord. (T/F)

(d) Dura mater is the outermost layer of the meninges. (T/F)

Question-6 (ICSE Biology 2021 Specimen)

The diagram below represents a layer of epidermal cells showing a fully grown root hair. Study the diagram and answer the questions that follow:

(i) Name the parts labelled A, B, C and D.

(ii) The root hair cell is in a turgid state. Name and explain the process that caused this state.

(iii) Mention one distinct difference between the parts labelled A and B.

(iv) Draw a diagram of the above root hair cell as it would appear when a concentrated solution of fertilizers is added near it.

Write down the functional activity of the following parts:

Differentiate between members of each of the following pairs with reference to phrases in brackets:

(i) Antibodies and Antibiotics (Source)

(iii) Serum and Vaccine (Composition)

Draw a labelled diagram of a Myelinated Neuron

Solutions of ICSE Biology 2021 Specimen

(i) Osmosis
(ii) Liver
(iii) Concave lens
(iv) Oxytocin
(v) Lenticels

(i) (B) Turgor pressure exceeds wall pressure.
(ii) (C) Thylakoids
(iii) (C) Renal pelvis
(iv) (D) Hypersecretion of Growth hormone
(v) (C) Calcium

(i) to kill the cells / destroy the enzymes
(ii) Remove chlorophyll / to decolorized it
(iii) Iodine
(iv) Blue black
(v) Brown/yellow

(i) Thylakoids (ii) Organ of Corti (iii) Lenticels (iv) Bicuspid Value (v) Loop of Henle [5]

(i) Name the defect shown in the diagram.
(ii) What are the two possible reasons that cause this defect ?
(iii) Name the type of lens used to correct this defect.
(iv) With the help of a diagram show how the defect shown above is rectified using a suitable lens.

(i) Lymphocytes of blood: Produce antibodies.
(ii) Leydig cells: Secrete male sex hormone testosterone.
(iii) Guard cells: Regulate the opening and closing of stomata in leaf to facilitate transpiration and exchange of gases.
(iv) Eustachian tube: Balance air pressure on either sides of the ear drum. So that ear drum can vibrate freely.
(v) Corpus luteum: Secretes hormones oesterogen, progesterone and relaxin.

Column A Column B
(i) Cranial nerves – 12 pairs

(ii) Leydig cells – Testosterone
(iii) Acetylcholine – Neurotransmitter
(iv) Spinal nerves – 31 pairs

(v) Sneezing – Natural reflex

(i) Odd term – Urineferous– Category Nervous System

(ii) Odd term – Pericardium, Category – Parts of blood vessels

(iii) Odd term – Spinal cord, Category – Parts of Neuron

(iv) Odd term – Centrosome, Category – Parts of plant cell

(v) Odd term – Seminiferous tubule, Category – Accessory glands of male reproductive system

(i) Animal cell. Centriole is present. [It can be a plant cell also as it is double layered (cell wall present) and astral rays are absent].

(ii) Metaphase. Unique feature is chromosomes are arranged at the equatorial plate (metaphasic) plate.

(v)

(i) (1) Anterior/Superior venacava (2) Dorsal aorta
(ii) Function of 5: Supply oxygenated blood to liver.
Function of 8: Cajry deoxygenated blood from posterior parts of the body to the right auricle of heart.
(iii) Importance of the blood vessel labelled 6: Blood vessel 6 is called Hepatic portal vein. It carries deoxygenated blood from intestine to liver. This blood contains excess glucose, some toxic substances etc. which are sent to liver where they are detoxified and the excess glucose is converted to glycogen and stored. This prevents these substances from directly entering the heart and damaging the heart.
(iv) Blood Vessel-6
(v)

(a)

(i) Genes: Genes are units of heredity that determine particular traits (e.g., colour of hair, blood group, colour of eye etc.)
(ii) Cytokinesis in plant cells: Cells in multicellular plants do not have centrioles. The division of cytoplasm occurs by the formation of a new cell wall in the equatorial regien at the end of anaphase. In telophase, new cellulose particles are gradually deposited in the equatorial zone. The particles extend on either side, from the centre towards the periphery (centrifugal) until it completely divides the cell. These particles fuse together to form a delicate plate membrane.
(iii) Guttation: The loss of water in the form of water droplets along the margins of leaves through hydathodes.
It takes place due to increased hydrostatic pressure that builds up within the cells. The wall pressure that develops in fully turgid parenchymatous cells force the water out.
(iv) Diapedes insipidus: The condition occurs due to lesser secretion of vasopressin (Anti-diuretic hormone) from the posterior lobe of pituitary gland. The disease is characterized by excretion of large amounts of urine and subsequent dehydration and thirst. No sugar or albumin is present in the urine. A person with severe diabetes insipidus may die due to dehydration if deprived of water for few days.

(v) Osmosis: It is the movement of water molecules from the region of its lower concentration to the region of higher concentration through semipermeable membrane.

(i) Transpiration.
(ii) The process in which plants lose water in the form of vapour from its aerial parts.
(iii) To prevent escape of the soil water as vapour.
(iv) A similar set up without a living plant.
(v)

1. Due to transpiration there is an upward movement of water so roots can absorb more water and thus minerals from soil.
2. The transpired water forms a cool blanket around the plant thus protecting it from the heat of sun.
(vi) 1. The stomata are sunken into pits.
2. The stomata are covered by hair.
3. The leaf is narrow to reduce the number of stomata.

1. Pituitary gland.
2. Thyroid gland
3. Pancreas
4. Adrenal gland
(ii) Thyroxine. It regulates basal metabolism of the body.
(iii) Islets of Langerhans.
(iv) Because it controls the secretions of all the other endocrine gland. Hypothalamus controls it.
(v) Adrenal medulla (part of Adrenal gland.)

(i) Urinary / Excretory system

2 – Left Ureters
4 – Sphincter muscle
5 – Urine is expelled from urinary bladder through urethra.

(iv) Urine main nitrogenous water present in it is urea.

(v)

A root hair gets turgid because of the absorption of water from the surrounding. Absorption of water by root hair is achieved by the process of osmosis. The concentration of water in the surrounding is more than that of the interior of the cell this causes the water from the surrounding to move in because of endosmosis.

Cell wall Cell membrane
The cell wall of a root hair is freely permeable and allows both salt and water to pass through. The cell membrane of a root hair is semi-permeable and does not allow large dissolved salt molecules to pass through.

(a) Glomerulus is involved in the process of ultrafiltration. The liquid part of the blood which is plasma including urea, salts, glucose filters out from the glomerulus into the renal tubule.

(b) Henle’s loop is involved in reabsorption of water and sodium ions.

(c) Ureter carries urine to the urinary bladder by ureteral peristalsis.


MATERIALS AND METHODS

Frequency of tail swishes

The tail swishing behaviors of zebras (Equus quagga), giraffes (Giraffa camelopardalis) and African elephants (Loxodonta africana) were filmed at Zoo Atlanta (Atlanta, GA, USA) horses (Equus caballus) were filmed at Falcon Ridge Stables in Woodstock, GA and dogs (Canis lupus familiaris) were filmed at a local dog park between the months of July and November. This study was approved by the Office of Research Integrity Assurance and conducted in accordance with all protocols filed under the Georgia Institute of Technology Institutional Animal Care and Use Committee. Tracker Video Analysis and Modeling Tool software (https://physlets.org/tracker/) was used to track the tail movements. MATLAB was used to calculate fits of the data using the least-squares method.

The number of periods to measure the frequency and amplitude of the swish were: elephant, 9 giraffe, 7 zebra, 7 horse, 11 and dogs, 8, 9, 5, 13, 17, 9, 16 and 9. The mass of the zoo animals, horse, Greyhound, Irish Setter and mixed breed dogs is the mass of the individual animal, measured in the past year by the animal's caretakers, while the mass of the other dogs is the average mass of that breed and gender. The body mass, tail length, tail swish frequency, tip speed and amplitude for each animal are shown in Fig. 2 and given in Table S1, and the sinusoidal fits for each animal's tail swing is given in Table S2.

The kinematics of tail-swishing. Relationships between body mass and (A) tail length L, (B) tail frequency f, (C) tail amplitude A and (D) tail tip speed u. Dashed line is fit of the data and error bars are the standard deviation of each measurement. In B, solid line is the natural frequency of the tail. The number of periods, N, used for calculating the frequency, amplitude and tip speed for each animal are given in Table S1. The data in A are only one measurement for each animal, as described in the Materials and Methods.

The kinematics of tail-swishing. Relationships between body mass and (A) tail length L, (B) tail frequency f, (C) tail amplitude A and (D) tail tip speed u. Dashed line is fit of the data and error bars are the standard deviation of each measurement. In B, solid line is the natural frequency of the tail. The number of periods, N, used for calculating the frequency, amplitude and tip speed for each animal are given in Table S1. The data in A are only one measurement for each animal, as described in the Materials and Methods.

Mosquito experiments

We obtained mosquitoes (Aedes aegypti) from the Centers for Disease Control and Prevention in Atlanta, GA, USA. The mammal tail simulator with the fan attachment consisted of a black, 18 cm long and 1.7 cm wide plastic blade attached to a DC-powered motor. The fan was attached to a plastic board and placed face down on a 30 cm tall, 19.5 cm inner diameter clear acrylic cylinder with open top face, as shown in Fig. 3A.


Introduction

The polar regions (the Arctic and Antarctic) are characterized by continuous light in the summer and almost total darkness, blizzards, scarcity of food and temperatures occasionally as low as −60°C in the winter. The Arctic is defined as the area north of the 10°C isotherm for July, whereas the Antarctic is the area south of the Antarctic Convergence (see Glossary) Arctic and Antarctic animals are those having their winter residency and main area of distribution within those boundaries (Box 1) (Irving, 1972 Blix, 2005). Probably because of the challenges imposed by this environment, the number of species that can cope with life in the polar regions is low, but most of those that prevail occur in large numbers. The effects of global warming are particularly felt in the polar regions, and an understanding of the needs of the animals therein and their tolerances to environmental change is greater than ever. This Review will focus primarily on the adaptations (see Glossary) of young and adults to low temperatures, and the effects of scarcity of food and lack of light during winter, as well as continuous light during summer, on animals that are permanent residents in polar regions.

The terrestrial Arctic animals discussed in this Review are the polar bear (Ursus maritimus), polar wolf (Canis lupus), Arctic fox (Vulpes lagopus), ermine (Mustela ermina), muskox (Ovibos moschatus), reindeer/caribou (Rangifer tarandus), Arctic hare (Lepus arcticus) and lemming (Dicrostonyx sp./Lemmus sp.). The marine Arctic animals that are discussed are the bowhead whale (Balaena mysticetus), narwhal (Monodon monoceros), white whale (Delphinapterus leucas), bearded seal (Erignatus barbatus), ringed seal (Pusa hispida), hooded seal (Cystophora cristata), harp seal (Pagophilus groenlandica), ribbon seal (Histriophoca fasciata) and walrus (Odobenus rosmarus).

In the Antarctic there are no land mammals, but there are marine mammals, such as the crabeater seal (Lobodon carcinophagus), Ross seal (Ommatophoca rossi), Weddell seal (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx), which are closely associated with the pack ice.

The true Arctic birds are the snowy owl (Nyctea scandiaca), raven (Corvus corax), rock ptarmigan (Lagopus mutus) and Arctic redpoll (Carduelis hornemanni), as well as some little-known seabirds such as the ivory gull (Pagophila eburnea) and Ross gull (Rhodo rosea). In Antarctica, there are no resident terrestrial birds, but resident marine birds, such as Emperor (Aptenodytes forsteri) and Adélie (Pygoscelis adeliaestethia) penguins, Antarctic petrels (Thalassoica antarctica) and snow petrels (Pagodroma nivea), are abundant.

In addition, there are multitudes of migratory mammals and birds that visit the polar regions during summer. The Arctic ground squirrel (Citellus parryi) and the Djungarian (or Siberian) hamster (Phodopus sungorus), for example, are hibernators that are not normally considered as truly Arctic mammals (and hibernation is not a common Arctic strategy). However, the range of these animals extends into the Arctic, where they have been much studied (Heldmaier et al., 2004). They will therefore be considered, in brief, in this Review, and some studies of other sub-polar species with obvious relevance for the true polar species are included.


What makes hair curly?

If you're a curly-haired individual or just an envious straight-haired person, you may wonder what exactly causes some strands to swirl whilst others simply stay smooth. It turns out there are two theories, according to a 2018 study published in the Journal of Experimental Biology.

The first hypothesis states that curls can be explained by a greater number of hair cells on the convex side of the hair follicle — that is, the outside edge of the curl — and fewer on the concave side — the inside edge. That relatively smaller number of cells on the inside creates a shorter edge, which pulls the follicle inwards, creating the curl.

The other theory suggests that differences between the cell lengths on the convex and concave sides of the strand of hair could explain curls. Similar to the first theory, the relative size difference between elongated cells on the outside and compact cells on the inside creates the curl.

Curly hair is thought to be better at keeping mammals warmer than just straight hair alone. In fact, straight hairs interwoven with curls creates the last line of defense against heat loss.

"The typical mammalian coat structure is that of a forest with shrubs," said study lead researcher Duane Harland, a senior scientist at AgResearch, one of New Zealand&rsquos largest corporate government research institutes. Straight hairs stick up to &ldquocreate a space near the skin" and "the finer curly hairs fill the space and trap air," Harland told Live Science.

Harland's study, however, only addressed curls in Merino sheep. It's hard to know for sure if insulation is what also drove some humans to develop curly locks. "The simple answer is that nobody knows specifically about human hair,&rdquo Harland said. "Our social aspect and ability to develop technology that replaces functions originally covered by biology, such as hats, make it hard to pin down."

That said, we can still learn a lot about the origins and biology of our own follicular features from our more furry friends, because if you go back far enough, our hair evolved from the same genetic origins. "Mammalian hair is ancient,&rdquo Harland said. It probably developed before the dinosaurs, Harland noted. (An analysis of 29 fossil skulls of archaic mammal relatives, the therapsids, suggests that these mammalian predecessors had fur, according to a 2016 study in the journal Scientific Reports.)

To test the two theories, Harland and his colleagues used sophisticated microscopy techniques to zoom in on sheep wool fibers and measure the differences between the number and size of the cells on the inside of the curve and those on the outside. Almost immediately, the team found evidence dispelling the idea that the number of cells creates the curl.

"We found evidence contradicting the theory that curvature results from there being more cells on the side of the fiber closest to the outside," he said. That&rsquos because, in all cases, he found the cells on the outside of the curve were longer, "which supports the theory that curvature is underpinned by differences in cell type length," Harland said.

Alas, it's not that simple. The story, as is so often the case with science, doesn't end here. "We have not got completely to the bottom of curly hair," Harland said. His study looked only at individual cross sections of sheep hair fibers under a microscope. That snapshot of hair could result from curvature, but it could also have some twisting forces, confusing the results, he said.

Even if those cross sections were good representations of hair strands as a whole, it doesn't mean the other theory — the one suggesting that cell numbers are the cause — is wrong. It could be that different hair on different animals is curly for different reasons.

"It would be pure hubris to declare that the situation is universal," Harland noted.

"So, there is scope for further discovery," he said. "It'd be great if other scientists out there were busy replicating and building on our study. Perhaps, they will find we got something wrong, hopefully only small things if anything, but that's science."


Do individual mammal hairs absorb water? - Biology

Chris Marshall noticed it when he snorkeled with manatees : even when he remained still and quiet in murky water, they kept a safe distance. It was as if the plant-eating mammals had a sixth sense that kept them posted on his location.

Marshall, who researched the manatees for his doctorate at the University of Florida, and his major professor recently discovered that manatees use small hairs on their body as antennae to pick up information about water currents, landscape and the presence of other animals.

Such an "underwater distance tactile system" is found in fish, which monitor underwater surroundings through twin lines of sensory pores along their bodies. But it is the first time the system has been found in mammals, say the scientists, whose paper on the research appears in the August issue of Brain, Behavior and Evolution.

"I've been with these animals in very murky conditions, and I've been very quiet and still, and they can always tell where I am," Marshall says. "They are using their small hairs, or vibrissae, to actually feel the pressure waves from my body."

It is far from the first fresh insight into these unique animals to come out of the University of Florida, where an informal manatee research group headed by scientist Roger Reep has earned a reputation as a leader in manatee science. Reep, an associate professor of physiological sciences with the UF College of Veterinary Medicine and the McKnight Brain Institute, has been studying the mammals for nearly two decades. The research has led to advances in the little-understood areas of manatee evolution, brain physiology and behavior.

Manatees are important to evolutionary biologists because they belong to a small and unusual group of herbivorous mammals — underwater counterparts to far more common land-grazing animals.

"What manatees are telling us about is the range of evolutionary potential because they are so weird," he says. "They are what evolutionary biologists refer to as ‘experiments in nature.'"

But the research also has important implications for conservation. Classified as an endangered species, an estimated 2,500 to 3,000 manatees live in Florida waters. Yet scientists continue to struggle with gaps in knowledge about what makes manatees thrive and how to protect them, both from natural threats such as red tides and man-made threats such as boat collisions.

Science Of The Strange

Manatees are large animals, with the biggest adults measuring as long as 13 feet and weighing as much as 3,000 pounds. Despite this heft, they have extremely small brains, with the largest attaining only the size of a small grapefruit. Also, unlike the complex, folded surface of other mammal brains, manatee brains are smooth. These abnormalities led early scientists to speculate that manatees were, to put it kindly, on the dim side of the animal kingdom. Writing in 1902, biologist Elliott Smith said, "The only parallel which can be found for the peculiar cases presented by the manatee and the dugong (a close manatee relative) is that presented in the brains of idiots."

Reep's research is calling that assumption into question. Animal intelligence is a notoriously sticky subject because no single measuring stick can be applied to all species. But Reep's work suggests that manatee brains are small for a good reason. He is also finding they are more complex than suggested by their appearance.

Manatees trace their evolutionary lineage to grass-eating land mammals that lived at least 50 million years ago. Their oldest ancestors were pig-like, four-legged animals that looked, improbably, like a cross between a hippopotamus and an otter, as one scientist has described it. As the animals evolved and entered the water, natural selection began to favor a larger body size because it helped the animal store heat, Reep says. Selection also favored a slow metabolism, which required the manatee to expend less energy moving around and consuming its exclusive diet of plants. Even as the manatee benefited from a large body, it had no natural predators, although sharks are thought to be an infrequent exception, Reep says. Manatees also never chased prey. So while size proved a benefit to the animal in evolution, it had no need for the intricate sensory systems and complex varying behaviors of mammals with bigger brains.

As evolution played out, in other words, the manatee's body grew, but its brain did not. "It's not that its brain is relatively small, it's that its body is relatively large," Reep explains.

To conclude from the manatee's brain size that it is less intelligent than other marine mammals is more human judgment than science — the manatee's brain has proved adequate for this slow and defenseless animal to persist to present times, Reep says. Further, Reep's dissections show that while the brain is indeed smooth on the outside, it is quite complex beneath the exterior. More recent work at other Florida institutions, meanwhile, has shown that manatees can be trained to perform simple tasks.

Part of the difficulty in measuring animal intelligence is that species perceive and interact with the outside world through vastly different channels — bees, for example, see and respond to infrared light completely invisible to humans. To a bee, in other words, a human's movements and decisions would seem strange indeed. Reep's recent research has begun to open a window into the manatee's unique world. One of his discoveries is that the manatee's cerebral cortex has numerous large clusters of nerve cells. Reep believes these clusters are tied directly to a highly developed sense that people can only begin to appreciate: the manatee's antenna-like hairs.

Although manatees' awkward, roly-poly bodies draw the eye, the hairs and "whiskers" around its face may be its more fascinating feature. Thinly distributed around its body, the hairs clearly aren't keeping the animal warm. Its long whiskers, meanwhile, seem more than cosmetic adornments.

Reep's research is revealing the role of these features. Late in the 1990s, he and colleagues published a series of papers highlighting how manatees use the whisker-like bristles on either side of their mouths as living cutlery to grasp and take in food. Manatees can also control their lips independently of one another and use them pre-hensiley, like giraffes. Contrary to what might be expected, these two features make the manatee a remarkably dainty diner. A close-up video Reep made of a manatee eating water hyacinth shows the manatee eating choice parts of the plant on one side of its mouth while simultaneously rejecting unwanted parts with the other, all at a pace of about two bites per second.

Homosassa Springs Wildlife State Park serves as a rehabilitation and refuge center for injured West Indian manatees. Many other manatees prefer to spend the winter months around these constant-temperature springs of the Homosassa River, making it an ideal place to study the creatures in their natural habitat.

Dainty Eater, And Other Surprises

Although manatees' awkward, roly-poly bodies draw the eye, the hairs and "whiskers" around its face may be its more fascinating feature. Thinly distributed around its body, the hairs clearly aren't keeping the animal warm. Its long whiskers, meanwhile, seem more than cosmetic adornments.

Reep's research is revealing the role of these features. Late in the 1990s, he and colleagues published a series of papers highlighting how manatees use the whisker-like bristles on either side of their mouths as living cutlery to grasp and take in food. Manatees can also control their lips independently of one another and use them pre-hensiley, like giraffes. Contrary to what might be expected, these two features make the manatee a remarkably dainty diner.

REEP'S RESEARCH HAS OTHERIMPLICATIONS FOR CONSERATION. FOR EXAMPLE, LEARNING ABOUT THE ANTENNA SYSTEM MAY INDIRECTLY HELP MANAGERS SAVE MANATEES BY ENABLING THEM TO IDENTIFY AND PRESERVE THE HABITAT THE ANIMALS NEED MOST.

A close-up video Reep made of a manatee eating water hyacinth shows the manatee eating choice parts of the plant on one side of its mouth while simultaneously rejecting unwanted parts with the other, all at a pace of about two bites per second.

"Manatees have a lot more fine motor control with their mouths than you might expect," Reep says. The manatees' sensory body hairs are also unique.

Although many residents and visitors to Florida journey to the state's clear springs to see them, manatees spend most or their lives in water stained by tannins or clouded with sediment, says Marshall, the former doctoral student in Reep's lab who is now an assistant professor of marine biology at Texas A&M University. Researchers had long puzzled over how the animals, which have relatively poor vision, find their way in these conditions, he says. Also puzzling to scientists was manatees' proclivity for taking advantage of water flow. For example, manatees often swim from an estuary into a river just as the tide starts coming in, Marshall says.

Marshall and Reep examined the anatomy surrounding individual hairs by dissecting carcasses of manatees that had been killed in boat collisions and stored at the Florida Marine Research Institute's necropsy laboratory in St. Petersburg. They found that each hair on the body is a tactile hair, with a specialized follicle and dense nerve connections. If these are anything like tactile hairs in other animals, they are surrounded by motion detectors called mechanoreceptors, with nerves connecting to the brain, the researchers say. Margaret Stoll, a biological scientist at UF, participated with Reep and Marshall in the latest research.

Marshall and Reep examined the anatomy surrounding individual hairs by dissecting carcasses of manatees that had been killed in boat collisions and stored at the Florida Marine Research Institute's necropsy laboratory in St. Petersburg. They found that each hair on the body is a tactile hair, with a specialized follicle and dense nerve connections. If these are anything like tactile hairs in other animals, they are surrounded by motion detectors called mechanoreceptors, with nerves connecting to the brain, the researchers say. Margaret Stoll, a biological scientist at UF, participated with Reep and Marshall in the latest research.

"When a hair is deflected, the mechanoreceptors on that side get squeezed, and they send a signal through a network of nerves to the brain," Marshall says. "So it's really an integral part of the sensory system of the animal."

People may feel a breeze or light touch with their body hair. The manatees' perceptions are apparently much more acute, allowing them to detect objects at greater distances and with greater specificity.

Bones And Boats

The manatee's unusual sensory system may help it navigate or find food, but it never evolved to deal with one of the animal's biggest modern threats: boats. When active, manatees ascend to the surface to get air about once every five minutes, which these days often puts them in the path of one or more of Florida's 900,000 boats. Each year, collisions with boats account for about 25 percent of roughly 300 manatee deaths. By the end of May this year, such collisions had already caused 54 manatee deaths, according to the Florida Marine Research Institute in St. Petersburg.

Marshall says manatees' antenna system appears to be no help because the animals receive information about boats too slowly for them to respond when the boats are traveling fast. The results of another Reep research project, however, may prove more useful to manatee protection. With an eye on the speed restrictions the state imposes on selected waterways to try to protect manatees, he and veterinary medicine doctoral student Kari Clifton are looking into the properties of manatee bone.

As with so many of the manatee's other attributes, the structure of its bone is unusual, Reep says. The rib bones in particular are extremely dense and heavy. It is thought that these heavy ribs provide ballast for the manatee like a weight belt for a scuba diver — ballast needed in part because the manatee's diet results in a lot of gas, Reep says. It might seem that such bone would be strong, but it is in fact quite brittle. The bulk of deaths due to boat collisions do not result from propeller cuts but rather from trauma and broken bones caused by the collision itself, Reep says.

Reep and Clifton are subjecting manatee rib bones to stress tests to find out their "energy of fracture," or just how strong they are. Reep hopes this will lead to a better understanding of when boats pose the most danger to manatees — and thus lead to more useful and effective regulations for boating in areas where manatees live.
"This will give us a scientific answer to the question of where the danger level is," Reep says. "Is there a safe, slow speed?"

Reep's research has other implications for conservation. For example, learning about the antenna system may indirectly help managers save manatees by enabling them to identify and preserve the habitat the animals need most.

"No one knows how these animals dig down into the substrate to get at the roots they eat, and my idea is they're doing it with these vibrissae around their mouths," Marshall says. "So this study is allowing us to understand the natural history of the animal, and by understanding the natural history we can better manage and protect it."


Q: Is providing extra insulin an effective curefor an individual who has diabetes that is caused by a h.

A: Diabetes is a condition in which the blood sugar rises above the normal level. There are two types o.

Q: Describe the origin and early evolution ofmammals.

A: The mammals belong to the class Mammalia and phylum Chordata. Mammals have mammary glands, three mid.

Q: What is the role of cork cambium?

A: Cork cambium is one of the defined layers of the bark of the vascular plants. It functions to add to.

Q: Water has key participation in organic reactions. What are examples of two types of organic reaction.

A: Water is important for life. It is a universal solvent. A cell has more than 70% water of its total .

Q: What do pure-breeding line produce?

A: Those plants that have been produced through repeated self - pollination and have become homozygous .

Q: Table 21.3 describes the cleavage sites of five different restrictionenzymes. After these restrictio.

A: An enzyme produced from the bacteria which recognizes specific base sequence in DNA and cut the DNA .

Q: Describe a method for isolating Cytophaga species from nature.

A: Cytophaga is a rod shaped, gram negative bacteria which is found in soil. This bacteria digests crys.

Q: What is geneticengineering?

A: Genetic engineering, also known as genetic modification. Use of genetic engineering in agriculture t.

Q: How do epigenetic traits differ from traditional genetic traits, such as the differences in the colo.

A: An epigenetic trait is a trait that is inheritable but does not cause any alterations in the DNA seq.


The Skin

The skin is remarkable not only because it is the body&rsquos largest organ. It is remarkable for other reasons as well. The average square inch of skin has 20 blood vessels, 650 sweat glands, and more than a thousand nerve endings. It also has an incredible 60,000 pigment-producing cells. All of these structures are packed into a stack of cells that is just 2 mm thick, or about as thick as the cover of a book. Although the skin is thin, it consists of two distinct layers, the epidermis and dermis, as shown in Figure (PageIndex<2>).

Figure (PageIndex<2>): The epidermis is the thinner outer layer of skin which is composed of tightly packed epithelial cells. The dermis is the thicker inner layer of skin that contains structures such as blood vessels, hair follicles, and sweat glands.

Outer Layer of Skin

The outer layer of skin is the epidermis. This layer is thinner than the inner layer, the dermis. The epidermis consists mainly of epithelial cells, called keratinocytes, which produce the tough, fibrous protein keratin. The innermost cells of the epidermis are stem cells that divide continuously to form new cells. The newly formed cells move up through the epidermis toward the skin surface, while producing more and more keratin. The cells become filled with keratin and die by the time they reach the surface, where they form a protective, waterproof layer. As the dead cells are shed from the surface of the skin, they are replaced by other cells that move up from below. The epidermis also contains melanocytes, the cells that produce the brown pigment melanin, which gives skin most of its color. Although the epidermis contains some sensory receptor cells, called Merkel cells, it contains no nerves, blood vessels, or other structures.

Inner Layer of Skin

The dermis is the inner and thicker layer of skin. It consists mainly of tough connective tissue and is attached to the epidermis by collagen fibers. The dermis contains many structures, as shown in the figure above, including blood vessels, sweat glands, and hair follicles, which are structures where hairs originate. In addition, the dermis contains many sensory receptors, nerves, and oil glands.

Functions of the Skin

The skin has multiple roles in the body. Many of these roles are related to homeostasis. The skin&rsquos main functions include preventing water loss from the body and serving as a barrier to the entry of microorganisms. Another function of the skin is synthesizing vitamin D, which occurs when the skin is exposed to ultraviolet (UV) light. Melanin in the epidermis blocks some of the UV light and protects the dermis from its damaging effects.

Another important function of the skin is helping to regulate body temperature. For example, when the body is too warm, the skin lowers body temperature by producing sweat, which cools the body when it evaporates. The skin also increases the amount of blood flowing near the body surface through vasodilation (widening of blood vessels), bringing heat from the body core to radiate out into the environment.

Hair is a fiber that is found only in mammals. It consists mainly of keratin-producing keratinocytes. Each hair grows out of a follicle in the dermis. By the time the hair reaches the surface, it consists mainly of dead cells filled with keratin. Hair serves several homeostatic functions. Head hair is important in preventing heat loss from the head and protecting its skin from UV radiation. Hairs in the nose trap dust particles and microorganisms in the air and prevent them from reaching the lungs. Hair all over the body provides sensory input when objects brush against it or it sways in moving air. Eyelashes and eyebrows protect the eyes from water, dirt, and other irritants.

Nails

Fingernails and toenails consist of dead keratinocytes that are filled with keratin. The keratin makes them hard but flexible, which is important for the functions they serve. Nails prevent injury by forming protective plates over the ends of the fingers and toes. They also enhance sensation by acting as a counterforce to the sensitive fingertips when objects are handled. In addition, fingernails can be used as tools.


The importance of the root hair in absorption of the water and mineral salts

The age of the root hair does not exceed a few days because, during the extending of the root through the soil , The epidermis cells are lost from time to time by the resistance of the soil particles, So, they are replaced by new ones continuously.

The suitability of the root hair for the absorption of the water and mineral salts

The root hair has a thin membrane that allows the penetration of the water and the salts through it, The number of the root hair is large to increase the surface area for absorption of the water and the salts from the soil.

The root hair secretes a sticky substance that helps the root to penetrate the soil particles, So the hairs draw the water forming a water membrane that facilitating the absorption process, The plasma membrane is the boundary that separates the living cell from its nonliving surroundings, The plasma membrane exhibits the selective permeability.

The cell membrane of the root hair has the selective permeability property to allow some types of the salts to pass according to the plant’s need and the energy needed for this process is obtained from the respiration process, The selective permeability is a process by which the cell membrane of the root hair allows some types of the salts to pass according to the plant’s need.

The concentration of the salt solution inside its vacuole is higher than the concentration of the salt solution in the soil to help the water to transport from the soil to the root hairs by the osmosis feature.

The osmosis feature is the transmission of the water molecules through the semi-permeable membrane from an area with a high concentration of the water to an area of low concentration of the water.

The high concentration of salt solution means that it contains a small amount of the water, so this solution has a low concentration of the water, The low concentration of the salt solution means that it contains a big amount of the water, so this solution has a high concentration of the water.



Comments:

  1. Faecage

    This is doubtful.

  2. Donall

    I believe you stand straight

  3. Tamirat

    And it is effective?

  4. Akinogrel

    Who knows.

  5. Rohon

    Are you kidding?

  6. Fenrilabar

    Yes, it's hard



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