Second half of content Flashcards
What is external respiration?
Gas exchange between the environment and lungs or gills.
What is internal respiration?
Transport of gases between blood and body tissue cells.
What is cellular respiration?
Breakdown of glucose in mitochondria to produce ATP.
What factors affect the rate of diffusion?
Surface area (↑), concentration gradient (↑), membrane thickness (↓).
Why do large animals need respiratory organs?
Diffusion is only efficient for very small animals.
How do gills support gas exchange?
Water flows over gill filaments; counter-current exchange maximizes O₂ uptake.
How do lungs support gas exchange?
Air enters alveoli where O₂ diffuses into blood and CO₂ diffuses out.
How do insects breathe?
Via tracheal system with spiracles; gases delivered directly to tissues.
How is avian respiration more efficient than mammals?
Unidirectional airflow and cross-current gas exchange in lungs.
Where is O₂ availability higher: sea level or high altitudes?
Higher at sea level.
Why is respiration harder in water than air?
O₂ is less soluble in water and more difficult to extract.
How does temperature affect dissolved O₂ in water?
Warmer water holds less O₂.
What is the path of air in the human respiratory system?
Trachea → Bronchi → Bronchioles → Alveoli.
What increases gas exchange in alveoli?
Large number and small size of alveoli surrounded by capillaries.
What is the role of the pleura?
Double-layered membrane that reduces friction during breathing.
What is tidal ventilation?
Breathing in and out in a back-and-forth (tidal) pattern.
What happens during inhalation?
Diaphragm contracts, rib cage expands, thoracic volume increases, air flows in.
What happens during exhalation?
Diaphragm relaxes, lung volume decreases, pressure rises, air flows out.
What brain regions control breathing?
Medulla and pons in the brainstem.
What does the Dorsal Respiratory Group control?
Normal breathing rhythm.
What does the Ventral Respiratory Group do?
Controls forceful breathing.
What do central chemoreceptors detect?
CO₂ and H⁺ levels in cerebrospinal fluid.
What do peripheral chemoreceptors detect?
O₂ levels in blood (carotid and aortic bodies).
What triggers increased breathing rate?
High CO₂ / low O₂ levels.
How is O₂ transported in the blood?
98% bound to hemoglobin in red blood cells.
What is the oxygen-hemoglobin dissociation curve?
Shows O₂ binding at high PO₂ and release at low PO₂.
What factors promote O₂ release from Hb?
High CO₂, low pH, high temperature (Bohr Effect).
In what three ways is CO₂ transported?
1) Dissolved in plasma, 2) Bound to Hb, 3) As bicarbonate (HCO₃⁻).
What is the Haldane effect?
Deoxygenated Hb binds CO₂ more readily than oxygenated Hb.
What happens in the pulmonary capillaries?
O₂ diffuses into blood, CO₂ diffuses into alveoli.
What happens in the systemic capillaries?
O₂ diffuses into tissues, CO₂ diffuses into blood.
What are the 5 main functions of the circulatory system?
1) Transport oxygen/nutrients/hormones
2) Remove waste (CO₂, nitrogen)
3) Regulate temperature
4) Support immune system
5) Maintain fluid/ion balance (homeostasis)
What type of circulatory system do simple animals like cnidarians use?
Gastrovascular cavity (uses diffusion)
What is an open circulatory system?
blood (hemolymph) is pumped into a body cavity and directly contacts organs (e.g. insects, arthropods)
What is a closed circulatory system?
Blood stays in vessels; more efficient; found in vertebrates and cephalopods
Describe single circulation (found in fish).
Blood passes through the heart once per cycle; lower pressure due to single pump
What circulatory system do amphibians and most reptiles have?
Partial ventricle division; allowing some mixing of oxygenated & deoxygenated blood
Describe double circulation (birds, mammals, crocodiles).
Complete separation of pulmonary & systemic circuits; enabling high pressure; efficient oxygen delivery
What do the atria and ventricles of the heart do?
Atria receive blood; ventricles pump blood
What do valves in the heart do?
Prevent backflow
AV valve: between atria & ventricles
Semilunar valve: between ventricles & arteries
What is systole and diastole?
Systole = heart contracts
Diastole = heart relaxes
myocardium
Self-excitable, rhythmic contractions, high endurance due to lots of mitochondria
What is the heart’s electrical conduction path?
SA node (pacemaker) → AV node (delay) → Bundle of His → Purkinje fibres
How does the sympathetic nervous system affect the heart?
Increases HR and BP using epinephrine/norepinephrine
How does the parasympathetic system affect the heart?
Slows HR using acetylcholine
What do arteries do?
Carry blood away from the heart; thick, high pressure; mostly oxygenated
What do veins do?
Carry blood to the heart; thin, low pressure; contain valves
What do capillaries do?
Enable gas and nutrient exchange with tissues
What are the 3 main functions of the lymphatic system?
1) Fluid balance
2) Fat absorption
3) Immune defense
What are the key components of the lymphatic system?
Lymph (fluid), lymph nodes (filter), lymphatic vessels (transport)
What molecule is used for oxygen transport in many invertebrates, and how does its color change with oxygenation?
Hemocyanin is used. It contains copper and turns blue (Cu²⁺) when oxygenated and colorless (Cu⁺) when deoxygenated.
What unique function does hemolymph serve in insect larvae?
Hemolymph functions as a hydraulic skeleton, helping with movement and structural support.
What is a hemocoel, and in what type of circulatory system is it found?
A hemocoel is the open body cavity in animals with an open circulatory system
What feature allows capillary beds in closed circulatory systems to regulate blood distribution?
Precapillary sphincters and vasomotion control blood distribution by regulating which capillaries receive blood flow.
What are the 4 basic digestive processes?
Breakdown, absorption, storage, and elimination (BASE)
What are carbohydrates, proteins, and fats absorbed as?
• Carbs → monosaccharides (glucose, fructose, galactose)
• Proteins → amino acids
• Fats → glycerol + fatty acids
What are macronutrients and micronutrients?
• Macronutrients: needed in large amounts (carbs, fats, proteins, calcium)
• Micronutrients: needed in small amounts (vitamins, iron, zinc)
What are essential nutrients?
Nutrients that must come from diet (cannot be made by the body)
How many essential amino acids, fatty acids, and vitamins are there?
9 amino acids, 2 fatty acids (omega 3 & 6), 13 vitamins
Vitamin A
- A: vision, bones, teeth, skin
Vitamin D
- D: bone growth, helps absorb calcium
Vitamin E
- E: antioxidant, protects cells
Vitamin K
- K: helps blood clotting (liver protein)
What is intracellular digestion?
Digestion inside cells using endocytosis & exocytosis
What is extracellular digestion?
Digestion in a cavity or tract outside cells
Name 4 types of feeders with examples.
• Fluid feeders: tapeworms, birds
• Suspension feeders: mussels, whales
• Deposit feeders: earthworms, crabs
• Bulk feeders: most animals
What are the 3 parts of a grasshopper’s gut?
• Foregut: mouth, crop, gizzard
• Midgut: stomach, gastric caeca
• Hindgut: ileum, colon, rectum, anus
How do carnivore vs herbivore digestive tracts differ?
• Carnivores: short tract, strong stomach acid
• Herbivores: long tract, large cecum, slow digestion
What’s the difference between monogastric and ruminant stomachs?
• Monogastric: 1 stomach (e.g., humans, pigs)
• Ruminant: 4 chambers (rumen, reticulum, omasum, abomasum — e.g., cows)
What are swallowing and peristalsis?
• Swallowing: reflex to move food into esophagus
• Peristalsis: wave-like muscle contractions moving food along digestive tract
What happens in the mouth, pharynx, and esophagus?
• Mouth: mechanical + chemical digestion (amylase)
• Pharynx: starts swallowing
• Esophagus: moves food to stomach via peristalsis
What does the stomach do?
Secretes gastric juice, digests food, creates chyme
What does the small intestine do?
Chemical digestion and nutrient absorption (has villi & microvilli)
What does the large intestine do?
Forms feces, absorbs water, supports gut microbiota
What are the digestive accessory organs?
• Teeth, tongue, salivary glands
• Liver (makes bile), gallbladder (stores bile), pancreas (enzymes & bicarbonate)
Name the major digestive enzymes and their functions.
• Amylase: breaks starch
• Protease: breaks proteins
• Lipase: breaks fats
• Nuclease: breaks nucleic acids
What’s the difference between anabolism and catabolism?
• Anabolism: builds complex molecules (needs energy)
• Catabolism: breaks down molecules (releases energy)
What is the role of bile in fat digestion and where is it produced and stored?
Bile emulsifies fats, breaking them into smaller droplets for easier enzymatic digestion. It is produced by the liver and stored in the gallbladder before being released into the duodenum.
What is the significance of chylomicrons in fat absorption?
Chylomicrons are protein-coated lipid droplets formed in intestinal mucosal cells. They transport absorbed fatty acids and monoglycerides via the lymphatic system into the bloodstream.
How do enterocytes in the small intestine enhance nutrient absorption?
Enterocytes are epithelial cells that form villi and microvilli (the brush border), dramatically increasing surface area. They also contain brush-border enzymes that complete nutrient digestion.
What enzymes are secreted by the stomach and what are their functions?
HCl: Activates pepsinogen and kills microbes
Pepsin: Begins protein digestion
Gastric lipase: Digests fats
Intrinsic factor: Facilitates vitamin B12 absorption
What are brush-border enzymes and where are they found?
Brush-border enzymes like lactase, maltase, and peptidases are embedded in the microvilli of small intestinal epithelial cells. They perform the final steps of carbohydrate and protein digestion.
What is chyme?
Chyme is a partially digested, semi-liquid mixture of food and gastric secretions formed in the stomach. It is gradually released into the duodenum for further digestion and absorption.
What is autocrine signaling?
A hormone acts on the same cell that secretes it.
What is paracrine signaling?
A hormone affects neighboring cells.
What is neuroendocrine signaling?
Hormones are released from neurons into the blood.
What is endocrine signaling?
Hormones are secreted into the bloodstream to act on distant target cells.
What are amine hormones derived from?
Tyrosine or tryptophan (amino acids).
Are amine hormones water-soluble or lipid-soluble?
Water-soluble; they bind to plasma membrane receptors.
Name some examples of amine hormones.
Epinephrine, norepinephrine, dopamine, melatonin, thyroid hormones.
Are protein/peptide hormones water- or lipid-soluble?
Water-soluble; they bind to plasma membrane receptors.
Give examples of protein/peptide hormones.
Insulin, glucagon, leptin.
Are steroid hormones water- or lipid-soluble?
Lipid-soluble; they bind to intracellular receptors.
What are steroid hormones derived from?
Cholesterol.
Name some steroid hormones.
Cortisol, testosterone, estradiol.
What does the hypothalamus do?
Produces releasing/inhibiting hormones and ADH/oxytocin.
What does the pineal gland secrete?
Melatonin.
What hormones does the anterior pituitary release?
ACTH, TSH, FSH, LH, prolactin, GH, MSH, endorphins.
What does the posterior pituitary do?
Stores and releases ADH and oxytocin.
What hormone is secreted by the parathyroid glands?
Parathyroid hormone (regulates calcium).
What does the thyroid gland secrete?
Thyroid hormones and calcitonin.
What does the adrenal cortex produce?
Cortisol, aldosterone, small amounts of androgens.
What does the adrenal medulla secrete?
Epinephrine and norepinephrine.
What hormones are secreted by the pancreas?
Insulin and glucagon.
What hormones are produced by ovaries?
Estrogen and progesterone.
What do testes secrete?
Androgens (e.g., testosterone).
What is the role of negative feedback in hormone regulation?
Hormones from target glands inhibit the hypothalamus and pituitary.
What does growth hormone do?
Stimulates growth, protein synthesis, and fat metabolism.
What do thyroid hormones regulate?
Metabolism and development.
What causes goiter?
Lack of iodine, which is needed for thyroid hormone synthesis.
What happens during acute stress?
Hypothalamus activates adrenal medulla → EPI/NOR → increases HR and glucose.
What happens during chronic stress?
Hypothalamus releases CRH → pituitary releases ACTH → adrenal cortex releases cortisol.
What does insulin do?
Promotes glucose uptake, glycogen synthesis, and fat storage.
What does glucagon do?
Stimulates glycogen breakdown and glucose release.
What does leptin do?
Signals satiety and energy status to the hypothalamus.
What gastrointestinal hormones regulate digestion?
Gastrin, secretin, and CCK.
What does parathyroid hormone do in calcium regulation?
Increases blood calcium by releasing it from bones and increasing kidney reabsorption.
What does calcitonin do in calcium regulation?
Lowers blood calcium by inhibiting bone resorption.
How are hydrophilic hormones stored?
In secretory vesicles until exocytosis, regulated by calcium.
How are hydrophobic hormones like steroids secreted?
They diffuse out of the cell immediately after synthesis—no vesicle storage.
What two hormones are released by the adrenal medulla in acute stress?
Epinephrine (75%) and norepinephrine (25%).
What are the pros of asexual reproduction?
Rapid reproduction, no need to mate, efficient in stable environments.
What are the cons of asexual reproduction?
No genetic diversity, low adaptability, offspring are clones.
What are the common types of asexual reproduction?
Budding, fission, fragmentation/regeneration, parthenogenesis.
What is parthenogenesis?
Development from an unfertilized egg.
Example: bees, reptiles.
What is the main advantage of sexual reproduction?
Genetic variation, better adaptability in changing environments.
How is genetic variation generated in sexual reproduction?
Independent assortment, crossing over, random fertilization.
What is simultaneous hermaphroditism?
An individual has both ovaries and testes at the same time.
What is sequential hermaphroditism?
An individual changes sex during life (e.g. clownfish).
Where does spermatogenesis occur?
In males, continuously from puberty.
What does each spermatocyte produce?
Four haploid sperm.
Where does oogenesis occur?
In females, starts before birth; one oocyte matures per cycle.
What hormone triggers ovulation?
LH (Luteinizing Hormone).
What does FSH do in females?
Stimulates follicle development.
What does estradiol do?
Promotes follicle and oocyte growth.
What does progesterone do?
Prepares uterus for embryo implantation.
What hormones regulate spermatogenesis?
FSH (supports sperm maturation) and LH (stimulates testosterone).
How do sperm and ovum differ?
Sperm: small and mobile; Ovum: large and immobile.
What does the sperm midpiece contain?
Mitochondria for energy.
What surrounds the ovum?
Zona pellucida and vitelline coat.
What is external fertilization?
Gametes released into the environment (aquatic species).
What is internal fertilization?
Occurs inside the female’s body.
What are oviparous species?
Lay eggs, little to no parental support.
What are viviparous species?
Live birth, embryo develops inside the body.
What is ovoviviparous development?
Eggs hatch inside parent’s body with little support (e.g. snakes).
What happens during fertilization?
Egg and sperm unite to form a zygote; diploid restored.
What is cleavage?
Rapid mitotic divisions forming morula → blastula.
What is gastrulation?
Formation of germ layers: ectoderm, mesoderm, endoderm.
What is neurulation?
Formation of the neural tube.
What is organogenesis?
Germ layers form organs and tissues.
What happens during growth and maturation?
Cell division, tissue specialization, and full organism development.
What hormone stimulates the development of a follicle in the ovary?
FSH (Follicle-Stimulating Hormone).
When are FSH and LH levels highest?
During ovulation.
What hormone stimulates the growth and development of the oocyte?
Estradiol.
What secretes estradiol before ovulation?
The developing follicle.
What secretes estradiol after ovulation?
The corpus luteum.
What is the function of estradiol in the uterus?
Thickens the endometrium.
What hormone is secreted by the corpus luteum to prepare the uterus for a fertilized egg?
Progesterone.
What causes the follicle to rupture and release the egg?
The LH surge.
What structure forms after the follicle ruptures?
Corpus luteum.
What is the role of the corpus luteum?
Secretes progesterone (and some estrogen) to maintain the uterine lining.
What happens if fertilization does not occur?
Corpus luteum degenerates, progesterone drops, and menstruation begins.
What is budding?
A new individual grows from the body of the parent (e.g. sponges, cnidarians)
What is fission?
One individual splits into two or more equal parts (e.g. cnidarians)
What is fragmentation / regeneration?
A body part breaks off and regenerates into a new individual (e.g. echinoderms)
Name the three processes that contribute to genetic diversity in sexual reproduction.
Independent assortment during meiosis I
Crossing over during prophase I
Random fertilization
What is the role of FSH in gametogenesis?
Stimulates spermatogenesis in males and follicle development in females
