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Chapter 12. Systematic Level of Animals

Higher Category: 【Biology】 Biology Index 

1. Cell

2. Tissue

3. Organ

4. Organ system

5. Individual: Homeostasis

6. Individual: Metabolic Regulation

7. Individual: Thermoregulation

8. Individual: Osmotic Control

1. Cell

⑴ Animals consist of about 200 kinds of cells

⑵ Cell theory

⑶ Cell type

① Epithelial cell

② Endothelial cell

③ Immune cell

④ Stromal cell

⑷ Extracellular Matrix

① Fibrous material

○ Collagenous fiber: The toughest. Composed of collagen. Tendon is the collagenous fiber for example. About 90% of extracellular substrate

○ Reticular fiber: Thin and branchy. Net shape

○ Elastic fiber: Elasticity ↑. Distribution in the vessel wall

② Substrate: No shape. Tenderness

○ Cement substrate: Stiffness

③ Glycosaminoglycans (GAG): About 5% of extracellular substrate

**2. Tissue

⑴ A group of cells with similar structure and function to perform common functions

⑵ Tissue = Cell + Extracellular Substrate + Tissue Fluid

⑶ Type 1. Epithelial tissue

① Dense monolayer or multilayer cell layer forming the inner or surface of organ, blood vessel, body cavity

② Function: Mechanical loss, pathogen invasion, fluid loss protection, environmental protection in the body, control of internal and external material exchange

③ One side anchored to the bottom, the other side exposed to body fluids or the environment

○ Protection, secretion and absorption function

○ Make up exocrine glands like sweat glands and digestive glands

④ Epithelial cells continue to fall off and are supplemented by cell division of stem cells in epithelial tissue

⑤ Kinds

○ Simple cuboidal epithelium: The surface layer appears rounded.

○ Example: Renal tubules, thyroid gland, salivary glands

○ Simple squamous epithelium

○ Example: Alveoli

○ Simple columnar epithelium

○ Example: Cells of the small intestine

○ Stratified squamous epithelium: Found on surfaces subject to abrasion.

○ Example: Keratinized type is mainly found in the skin; non-keratinized type is found in the mouth, esophagus, vagina, and anus

○ Stratified columnar epithelium

○ Pseudostratified ciliated columnar epithelium: Actually a single layer

○ Example: Cilia of the fallopian tubes, cilia of the bronchi

⑥ Function

○ Exchange: Simple squamous epithelium

○ Characteristic: Molecules exchange smoothly through gaps between cells

○ Location: Lungs, vascular endothelium

○ Transport: Simple cuboidal and simple columnar epithelium

○ Characteristic: Tight junctions prevent exchange between cells; cell membranes form folds and villi to increase surface area

○ Location: Small intestine, kidney, some exocrine glands

○ Cilia: Simple cuboidal and simple columnar epithelium

○ Characteristic: One side is covered with cilia that move fluids along the surface

○ Location: Nose, bronchi and upper respiratory tract, female reproductive tract

○ Protection: Stratified squamous epithelium

○ Characteristic: Cells are tightly connected by numerous desmosomes

○ Location: Epidermis exposed to the external environment, such as skin and inner surfaces of the mouth

○ Secretion: Simple columnar, cuboidal, and polygonal epithelium

○ Characteristic: Protein-secreting cells are filled with membrane-bound secretory granules and abundant rough endoplasmic reticulum; steroid-secreting cells contain lipid droplets and abundant smooth endoplasmic reticulum

○ Location: Exocrine glands like the pancreas, sweat glands, and salivary glands; endocrine glands like the thyroid and gonads

⑷ Type 2. Connective tissue

① Function to bind or support organs and tissues, composed of cells embedded in substrates, and also act as physical barrier

○ Substrate consists of fiber and tissue fluid

② Coarse connective tissue (e.g., Subcutaneous)

○ Consists of universal connective tissue, fibroblasts and substrates

○ Matrix: Gels; More matrix than fibers and cells

○ Substrate: Collagen and elastin fibers are loosely interwoven and also contain reticulated fibers

○ Supports epithelial tissue and holds underlying tissues and organs

○ Location: Skin, around blood vessels and organs, under epithelium

③ Fibrous connective tissue

○ Forms tendons and ligaments, composed of fibroblasts and substrate

○ Substrate: Dense collagen fibers arranged in parallel

○ Matrix: Most of the fiber rather than the matrix

④ Adipose tissue

○ Store fat in the form of fat droplets

○ Function: Connect skin to infrastructure, support organ, insulate, and save energy

○ Class 1. White fat

○ Large fat droplets exist

○ Has a small amount of protoplasts, few substrates and fibers

○ Low organelles, little blood supply

○ Function: Fat storage

○ Class 2. Brown fat: Brown due to blood flow

○ Many mitochondria, rich in blood supply

○ Function: Non-vibration heat production

○ Brown fat is observed in the armpit and neck area of infants

○ It gradually degenerates as an adult and increases with low temperature acclimation.

○ 1^st. The norepinephrine from the sympathetic nervous system activates the GPCR.

○ 2^nd. Increased cAMP and PKA during signal transduction

○ 3^rd. PKA acts on ligase to oxidize fatty acids

○ 4^th. cAMP and oxidized fatty acids produce thermogenin

○ 5^th. Thermogenin generates heat in mitochondria through uncoupled respiration.

○ Recent studies have revealed the presence of brown adipose tissue in adults, leading to research aiming to use it as an index for obesity.

○ Some papers define brown fat as adipose tissue that expresses UCP-1 (uncoupling protein 1).

○ Obesity: Born with a similar number of fat cells at birth

○ Childhood obesity: Fat cell number increase

○ Adult obesity: Fat cell enlargement

○ Fat cell location varies by age and gender

Figure 2. White fat (left) and brown fat (right). (A) indicates droplets

⑤ Blood

○ Cell composition: Red blood cells, white blood cells, platelets

○ Substrate: Plasma

○ Oxygen and nutrient transport, immune function to cope with infection

⑥ Cartilage

○ Chondrocytes Differentiate into Soft oesteocytes

○ Soft oesteocyte Secretes Substrate

○ Cartilage supports joint and has fluidity

○ Blood vessels are not distributed, so much time is needed to repair the damage

○ Cartilage Substrate (Gel State): Consists of water (70%), type II collagen, hyaluronic acid, chondroitin sulfate, glucosaminoglycans, proteoglycans, etc.

○ Location: Articular surface, spine, ear, nose, pharynx

○ Arthritis

○ 1^st. Substrate of cartilage has -OH group (due to glycoprotein) and has elasticity while holding moisture

○ 2^nd. Reduction of Substrate in Old Age

○ 3^rd. Inflammation of joints after loss of elasticity and injuries

⑦ Bone

○ Hard connective tissue due to calcium salts

○ Osteoblast: Secrete substrate composed of collagen fiber and calcium phosphate

○ Osteoclast: Decompose bone

○ Oesteocyte: Maintain solid bone substrate

○ Lack of dietary calcium leads to the use of calcium in bone

⑧ Related disease: Marfan syndrome

⑸ Type 3. Muscle tissue

① Contractile tissue, composed of muscle cells (muscle fibers)

② Actin and myosin protein interact to muscle contraction

③ 3 types: Skeletal muscle, heart muscle, smooth muscle

○ Skeletal muscle: Voluntary movement, parallel arrangement, horizontal pattern, multinucleate, non-differential

○ Heart muscle: Involuntary movement, pruning arrangement, horizontal pattern, mononucleate, differential

○ Smooth muscle: Involuntary movements, fusiform, flat pattern, mononucleate, differential

○ Degeneration of sarcomeres, absence of T-tubules

⑹ Type 4. Nerve tissue

① Transmitting nerve signals from one part of the animal to another

② Composed of neurons. Brain and spinal cord composition

③ Neurons: A sense of stimulation. Stimulus information processing. Send exercise command

④ Glial cell: Nourishing neurons. Insulator. Involved in neuronal formation

⑤ Most nervous system cells do not divide

3. Organ

⑴ Composed of several (≥ 2) tissues for independent functions

⑵ Exists in all animals except sponges

⑶ One organ can belong to multiple organ systems

① Example: The pancreas plays an important role in both the endocrine and digestive systems.

⑷ Example: Heart, stomach, lungs, etc.

4. Organ System

⑴ Example: Digestive system, respiratory system, circulatory system, endocrine system, nervous system, exercise system, immune system, etc.

5. Individual : Homeostasis

⑴ Animal classification according to the internal environment control method

① Regulator: Uses internal control mechanisms to reduce internal changes caused by external fluctuations

② Conformer: Changes the internal environment according to the external environment

⑵ Negative feedback control: Mechanisms of change reduction to eliminate the causes of environmental changes in the body

① Class 1. Feedback inhibition: Feedback circuits interfere with enzyme and metabolic mechanisms

② 1-1. Concerted feedback inhibition

○ Each final product must be above a certain concentration to inhibit the enzyme

○ Enzyme has more than one allosteric site

③ 1-2. Cumulative feedback inhibition

○ Each final product partially inhibits the enzymes involved in the initial reaction

○ If the sum of each amount of the final product exceeds a certain level, the total enzyme is inhibited

④ Class 2. Feedback repression: Feedback circuitry interferes with gene transcription (↔ induction)

⑶ Positive feedback: a mechanism that amplifies changes by increasing the factors causing the change in the internal environment; it does not contribute to homeostasis.

① Example 1. Blood clotting

② Example 2. Uterine contractions at birth

③ Example 3. Reproductive cycle: Estrogen

④ Example 4. Neuronal action potential

⑷ Change in homeostasis

① Set points and normal ranges for homeostasis may vary for different environments

○ Example: Most animals have lower body temperatures when they are sleeping than when they are awake

② One way to change the normal range of homeostasis is the process of adapting to changes in the external environment.

○ Example: Physiological changes in mammals ascending from sea level to highlands include increased blood flow to the lungs and increased red blood cell production.

6. Individual: Metabolic regulation

⑴ Bioenergetics: determines how much food an animal requires and limits its behavior, growth, and reproduction.

① Metabolic rate: The amount of energy used per unit time, the amount of energy required for the entire biochemical reaction for a given time

② Energy strategy

○ In general, endothermic animals have a much higher metabolic rate than ectothermic animals.

○ Endothermic animals can sustain intense activities (e.g., long-distance running, active flight) for longer periods than ectothermic animals.

○ In general, endothermic animals have lower tolerance to internal temperature fluctuations and require a greater food intake compared to ectothermic animals.

⑵ Effect on metabolic rate

① Size and metabolic rate

○ Excessive size of the animal limits mobility

○ Larger animals increase energy cost per body mass

○ The larger the animal, the more adequate the exchange system for exchanging material (eg: Circulatory system)

○ body mass index (BMI)

○ Defition: Weight (kg) divided by height (m) squared

○ BMI ≥ 30: Obesity. BMI <18.5: Low weight

② Activity

○ Maximum metabolism rate: Occurs during intense activity and is inversely proportional to duration of activity

○ Minimum metabolic rate: Promote life-sustaining functions such as cell maintenance, respiration, and heart rate, divided into basic metabolic rate and standard metabolic rate

○ Basal metabolic rate (BMR): The metabolic rate of an endothermic animal that is resting, has an empty stomach, and does not grow under stress. Determined within the environmental temperature range.

○ Example: Adult men 1600-1800 kcal / day, adult women 1300-1500 kcal / day

○ Standard Metabolic Rate (SMR): the metabolic rate of an ectothermic animal that is at rest, not eating, and not under stress at a specific temperature. The metabolic rate varies depending on the environmental temperature.

③ Animal form

○ Streamlined animal body design reduces frictional resistance when moving

○ The flat body design has a large surface area per unit volume, which is advantageous for mass exchange.

⑶ Energy balance: Percentage of items where energy is used

① Endothermic Animal Energy Balance

○ Significantly consumes a large percentage of energy

○ The proportion of energy spent on thermoregulation is inversely related to body size.

② Ectothermic Animal Energy Balance

○ Very low percentage of energy spent on thermoregulation

○ Significantly less energy expenditure than endothermic animals of the same size

⑷ Dormancy and energy conservation

① Hibernation: Adaptation to winter cold and food shortage

○ Example: Hibernating Ground Squirrel: Lowers body metabolism by lowering body temperature

② Estivation: An adaptation to prolonged periods of high temperatures and limited water availability.

③ Daily torpor: All endothermic animals that undergo daily torpor are small in size. It is considered an innate cycle regulated by the biological clock.

○ Example: Bats feed at night and enter torpor during the day. They continue to exhibit daily torpor even when food is continuously available.

7. Individual : Thermoregulation

⑴ Necessity of Thermoregulation

① Necessity 1. The temperature at which the enzyme is active is limited, so most cell functions are limited to a narrow temperature range.

○ The average human body temperature ranges from 37 to 37.8°C.

○ A temperature below this range can lead to hypothermia.

○ A temperature above this range can cause brain damage.

② Necessity 2. Heat continues to develop in life.

○ Standard adult men produce 87 W for sleep, 115 W for rest or office work, 230 W for bowling, 440 W for severe physical labor

○ Adult women produce about 15% less heat because their bodies are smaller than in adult men

③ Necessity 3. Heat exchange between the skin and the external environment (conduction, convection, radiation, evaporation)

○ The key to thermoregulation is to equalize heat gain and heat loss.

○ Animals perform thermoregulation to reduce heat exchange as a whole

⑵ Classification of animals based on thermoregulation

① Endotherm: an organism that regulates its body temperature using heat produced internally.

② Ectotherm: an organism that regulates its body temperature using external sources of heat.

③ Homeotherm: generally an endothermic animal; maintains a constant body temperature.

④ Poikilotherm: generally an ectothermic animal; body temperature varies within a certain range.

⑤ Both endothermic and ectothermic animals regulate body temperature by controlling blood flow.

⑶ Methods of Thermoregulation

① Method 1. Active heat production: generally applies only to endothermic animals

○ Method 1-1. Shivering thermogenesis: heat production through muscle activity such as movement or shivering

○ Method 1-2. Non-shivering thermogenesis: involves brown adipose tissue

○ Method 1-3. Thyroxine and metabolic heat

○ Some large reptiles can increase their metabolic rate through shivering

② Method 2: Evaporative cooling: generally applies only to endothermic animals

○ Panting

○ Sweating: observed in many terrestrial animals; they have sweat glands regulated by the nervous system

○ Saliva spreading: observed in some kangaroos and rodents

○ Regulation of evaporative cooling through changes in the amount of mucus on the body surface

③ Method 3: Behavioral responses

○ Ectothermic animals rely more heavily on behavioral thermoregulation than endothermic animals

○ Honeybees: use thermoregulation mechanisms based on social behavior; on cold days, the density of the swarm and heat production increase

④ Method 4: Heat and adaptation

○ Surface area: species living in cold environments tend to have smaller surface areas

○ Insulation: reduces heat flow between the animal and the environment

○ Examples: fur, feathers, fat layers

○ Circulatory adaptations: adjust the volume of blood flow between the body core and the skin in response to changes in environmental temperature

○ Vasodilation: increases blood flow to the skin surface, enhancing heat loss to the environment

○ Vasoconstriction: decreases blood flow to the skin surface, reducing heat loss

○ Countercurrent heat exchange: a system that minimizes heat loss

Figure 6. Example of countercurrent heat exchange

○ Adjacent blood vessels carry blood in opposite directions to maximize heat transfer.

○ Some of the heat from arterial blood flows into venous blood, helping to maintain core body temperature.

⑤ Method 5: Acclimatization in thermoregulation

○ Acclimatization in endothermic animals:

○ Example 1: Adjusting the degree of insulation (e.g., growing thicker fur in winter and shedding it in summer)

○ Example 2: Seasonal changes in the capacity for metabolic heat production

○ Acclimatization in ectothermic animals: often involves adjustments at the cellular level

○ Example 1: Producing enzyme variants with the same function but different optimal temperatures

○ Example 2: Maintaining membrane fluidity across various environmental temperatures by altering the ratio of saturated to unsaturated fats

○ Example 3: Some organisms in extremely cold environments produce antifreeze compounds to lower the freezing point

⑷ Application 1: Automatic Thermoregulation in Vertebrate: The hypothalamus in the diencephalon regulates body temperature

Figure 7. Automatic Thermoregulation Machanism in Hypothalamus

① Set point

○ The hypothalamus is the brain region responsible for temperature regulation.

○ It compares the body’s internal temperature to the set point using internal thermoreceptors → detects cold or heat

② Use of feedback information

○ The hypothalamus stimulates the autonomic nervous system and the pituitary gland

○ When the hypothalamus detects cold → vasoconstriction in the skin reduces blood flow to the surface, shivering occurs → heat generation

○ When it detects heat → vasodilation increases skin blood flow, panting occurs → heat loss

③ Function 1: Heat acts as a defense mechanism against infection

○ Pyrogens raise the set point

○ During infection, macrophages secrete interleukins → hypothalamic set point increases → body temperature rises → immune enzymes become more active and microbial growth is inhibited

④ Function 2: Lowering the set point can conserve energy

⑸ Application 2: Drosophila and Heat Shock Proteins

① HSF (heat-shock factor) binds to HSE (heat-shock element) upstream of the HSP70 gene, inducing HSP70 expression

② HSF proteins gain binding activity to HSE in response to heat shock

8. Individual : Osmotic control

⑴ Osmotic Control Challenge: Moisture Balance of Various Animals

① Classification according to the method of maintaining water balance

○ Osmoconformers: animals that do not actively regulate their internal osmolarity. There is minimal net movement of water.

○ Osmoregulators: animals that maintain an internal osmolarity different from their external environment. Continuous energy expenditure is required.

② Osmotic Control of Seawater and Freshwater Animals

○ Sea animals: Water intake with high salt concentration, water leaks from the body surface by osmosis → Salt discharge from gills, small amount of urine with high salt concentration

○ Freshwater animals: Water intake with low salt concentration, water inflow into body surface by osmosis → Salt intake from gill, large amount of urine with low salt concentration

③ Water bear: Trehalos protects cell membranes and proteins during dehydration

⑵ Energetics of Osmotic Control: Saving energy

① Adapts body fluids to the salinity of the habitat to save energy consumed to balance water and solutes

② Transport epithelium: Take saline as an example.

○ Carrier epithelial cells in charge of solute transport consist of one or several layers

○ Large surface area in the form of complex tubes

○ Example: Seagulls consume 50% of the water they drank through the saline while removing 80% of salt

③ Countercurrent exchange

○ The direction of blood flow is opposite to the direction of salt excretion in the lumen of the secretory tubule.

○ This countercurrent system maintains a salt concentration gradient along the entire length, promoting the movement of salts from the blood into the tubule.

⑶ Osmoticity of the human body

① Water inflow (/ day)

○ Drink Intake: 1250 mL

○ Water of food: 1000 mL

○ Metabolic generation: 350 mL

○ Total inflow: 2600 mL

② Moisture Outflow (/ day)

○ Unconscious loss (lungs, skin): 900 mL

○ Sweat: 100 mL

○ Feces: 100 mL

○ Urine: 1500 mL

○ Total Outflow: 2600 mL

③ Osmotic homeostasis

Table 1. Osmotic concentration of various ions in the human body

④ Fluctuations in fluid volume and osmolarity

Table 2. Fluctuations in fluid volume and osmolarity

○ Extracellular fluid volume (ECF): Increasing fluid volume increases ECF, while decreasing it decreases ECF

○ Intracellular Fluid Volume (ICF): Increasing osmolality reduces ICF, while decreasing it decreases ICF

⑷ pH Homeostasis in the Human Body: A type of osmotic homeostasis

① Distribution of pH in the human body

Table 3. Distribution of pH in the human body (ref)

② Type 1. CO₂/HCO₃^- Buffer System: Open buffer system, most effective

○ CO₂ + H₂O ⇌ HCO₃^- + H⁺, pK_a = 6.1

③ Type 2. Protein Buffer System

○ protein·H⁺ ⇌ protein + H⁺, pK_a = 4 ~ 12

④ Type 3. Phosphate Buffer System

○ H₂PO₄^- ⇌ HPO₄^2- + H⁺, pK_a = 6.9

⑸ Edema

① Defition: Swelling caused by the movement of water from the blood into tissue fluid

② Cause 1. Sleep after eating high salt: Ramen broth)

○ 1^st. The kidneys do not work and salt is not released well

○ 2^nd. Salin accumulation in the blood

○ 3^rd. Blood delivers salt to tissues for osmolality

○ 4^th. Osmotic pressure increases water content in tissue

○ 5^th. Edema occurs

③ Cause 2. Kidney disease

○ 1^st. Kidney does not function smoothly and cannot release salt well.

○ 2^nd. Salin accumulation in the blood

○ 3^rd. Blood delivers salts to tissues for osmolality

○ 4^th. Osmotic pressure increases water content in tissue

○ 5^th. Edema occurs.

④ Cause 3. Fasting

○ 1^st. Reduced concentration of albumin, a temporary energy source in the blood

○ 2^nd. Blood Osmotic Pressure Reduction Effect

○ 3^rd. The presence of net water movement from the blood to tissue fluid

○ 4^th. Edema occurs

⑤ Cause 4. Exercise

○ 1^st. Increased blood pressure

○ 2^nd. The presence of net water movement from the blood to tissue fluid

○ 3^rd. Edema occurs

Input: 2015.7.16 09:46

revisions: 2019.9.14 23:04