Key Terms

Endoderm

Present in Diploblastic and triploblastic

Responsible for: Digestive Lining, Respiratory lining, Liver, Pancreas, Bladder

Ectoderm

Present in Diploblastic and triploblastic

Responsible for: Nerves, Skin, Nails, Hair

Mesoderm

Present only in triploblastic

Responsible for: Heart, Kidneys, Bones, Muscles, Blood Cells, Blood Vessels.

Protostomia

Mouth develops first

Deuterostomia

Anus develops first

Catabolism

Breaking down complex molecules into smaller ones to release energy

Anabolism

Building new molecules to repair and build larger structers

Homeostasis

• An active internal maintenance of steady state conditions around a set point.

  • We use metabolic processes to actively maintain homeostasis

  • Homeostasis relies on metabolism to provide the energy and building blocks needed to regulate body temperature, pH, and other vital functions.

Metabolic Rate

The amount of energy an organism uses per unit of time.

Direct Calorimetry

Measured in calories/day or kilocalories/hour or some combination of cal/time

Direct calorimetry measures heat produced by an organism directly.

Indirect Calorimetry

Measured in CO2/min or oxygen/time

estimates metabolic rate from oxygen consumption or carbon dioxide production.

Basal metabolic rate

Standard Metabolic Rate

The minimum metabolic rate of an ectotherm measured at rest, fasted, and at a specified

Active metabolic rate

The metabolic rate of an animal during maximal sustained activity/exercise

Field metabolic rate

The average metabolic rate of an animal measured under natural, free-living conditions/in the wild.

Basal metabolic rate

The minimum metabolic rate of an endotherm measured at rest, fasted, and within its thermal neutral zone.

Endotherm

An animal that generates and regulates most of its own body heat metabolically.

Thermal regulators, humans

Ectotherms

An animal whose body temperature is largely determined by the external environment.

Thermal conformers, fish

Whole Body Metabolic Rate

The total metabolic rate of an entire organism, not adjusted for body size.

Helpful for:

• Comparing energy budgets between individuals of different sizes (e.g., how much food does this animal need per day?)

• Calculating daily caloric requirements & nutrition 

• Ecological energetics: how much energy an organism draws from its environment

Mass-Specific Metabolic Rate

• Metabolic rate expressed per unit of body mass, allowing comparison between animals of

  different sizes.

• Used to compare metabolic intensity 

  • Mass-specific rate reveals that small animals burn dramatically more energy per gram of tissue than large animals, despite having lower whole-body rates

  • Helpful for:

    • Comparing tissue-level or cellular metabolic activity

    • Understanding metabolic efficiency 

Metabolism

• the sum of all chemical processes in the body → Catabolism + Anabolism  

• Through metabolic processes, animals are able to maintain internal steady state conditions which is called homeostasis. 

• We measure metabolism by looking how the body is using energy, per unit of time….either directly (heat produced) or indirectly (O2 consumed, CO2 produced, etc.). This is the Metabolic Rate. 

• Methods of measuring metabolic rate vary between the experimental conditions or species involved - examples include: Basal, Standard, Routine, Active, and Field Metabolic Rates

• Metabolic Rate is influenced by body size, environmental conditions, thermal regulatory status, etc. 

• Gram for gram, smaller body size occurs higher metabolic costs.

Carbohydrate/Monosaccharides

Provide quick energy (ATP!) and help with structural support (cellulose, chitin)

Protein/Amino Acids

Carry out many cellular functions (enzymes, cell membrane proteins), used in structural support (collagen), movement (actin, myosin)

Lipids/Fatty Acids

Provide long-term energy storage, form cell membranes, and play roles in hormones and cellular insulation.

Phyla that uses ONLY intracellular digestion

Porifera, they use phagocytosis to digest

Phyla that use intra and extracellular digestion

• Cnidarians do both intra and extracellular

  • Extracellular: Cells along the ENDODERM release digestive enzymes into the central cavity…starts to make a prey smoothie. 

  • Intracellular: Cells lining the cavity absorb the half-digested food particles. Finish digesting them inside the cells! 

• Playhelminthes are also both intra and extracellular! 

  • Some digestion happens extracellularly, but is completed intracellularly.

  • Extracellular: Release digestive enzymes intro/onto prey to start the process. Slurps prey into the body cavity via pharynx.

  • Intracellular: Smaller food particles are absorbed by phagocytosis in cells lining the intestine.

Phyla that use extracellular digestion

Arthropods, Vertebrata, Annelids, Echinoderms, Rotifera, Nematodes, Mollusca

Digestion

The mechanical and chemical breakdown of food into smaller molecules that can be absorbed

Absorption

The uptake of digested nutrients across the gut lining into the bloodstream or body tissues.

Aerobic Respiration

Aerobic respiration uses oxygen to fully break down fuel for a high ATP yield.

Anaerobic Respiration

Anaerobic respiration breaks down fuel without oxygen, yielding far less ATP.

Glycolysis

The metabolic pathway that breaks glucose down into pyruvate in the cytoplasm, yielding a small net amount of ATP.

Citric Acid (Krebs) Cycle

A series of reactions in the mitochondrial matrix, producing electron carriers (NADH, FADH2), CO2, and a small amount of ATP.

Oxidative Phosphorylation

The production of ATP using energy released as electrons pass through the electron transport chain, driving ATP synthase.

Electron Transport Chain

A series of protein complexes in the inner mitochondrial membrane that pass electrons and pump protons to build a gradient used for ATP synthesis.

Lactic Acid

The end product of anaerobic glycolysis in animal cells when oxygen is limited.

Pyruvate

The end product of glycolysis, which can enter the mitochondria for aerobic respiration OR be converted to lactic acid

Intracellular digestion

Digestion that takes place inside individual cells after they engulf food particles.

Chemical digestion

The enzymatic breakdown of food molecules into smaller subunits.

Extracellular digestion

Digestion that takes place outside of cells, typically within a digestive cavity or tract.

Complete digestive system

A digestive tract with two openings (mouth and anus), allowing one-way, specialized food processing.

Incomplete digestive system

A digestive tract with a single opening that serves as both mouth and anus.

Amylase

An enzyme that breaks down starch into smaller sugars.

Pepsinogen

The inactive precursor of pepsin, located in the stomach, activates into pepsin in low pH conditions

Pepsin

A stomach enzyme, active in acidic conditions, that breaks down proteins. Comes from pepsinogen

Gastrin

A hormone that stimulates gastric acid secretion and stomach motility.

Food in stomach → vagus nerve stimulated → Gastrin Secreted

Bicarbonate

An ion secreted by the pancreas, to neutralize acidic chyme entering the small intestine.

Secretin

A hormone released by the duodenum in response to acidic chyme that stimulates the pancreas to release bicarbonate.

Cholecystokinin (CCK)

A hormone released by the duodenum in response to fats and proteins that triggers gallbladder contraction to drip bile into the small intestine.

Gastric Inhibitory Peptide (GIP)

A hormone released by the small intestine that asks the pancreas to secrete insulin. Also inhibits gastric acid secretion and motility. Preps for cellular sugar absorption

Duodenum

The first section of the small intestine, where chyme mixes with bile and pancreatic

enzymes. Much digestion & a little absorption

Jejunum

The middle section of the small intestine and the primary site of nutrient absorption.

Ileum

The final section of the small intestine, which absorbs remaining nutrients along with

vitamin B12 and bile salts.

Cecum

A pouch at the junction of the small and large intestine that is important for fermentation in many herbivores

Bile salt

A compound produced by the liver that emulsifies fats, aiding their digestion and absorption

Micelle

A small aggregate of bile salts and lipids.

Lipase

An enzyme that breaks down triglycerides into fatty acids and monoglycerides.

Chylomicron

Formed in intestinal cells; triglyceride repacked with a protein coat allowing it to move easily through the body

Triglyceride

A lipid made of glycerol bonded to three fatty acids; the main form of stored fat.

Circulation

Pressure driven flow of fluids that rapidly transports various commodities around the body

Phyla with circulatory systems

mollusca, annelida, arthropoda, echinodermata and vertebrata have circulatory systems

What are the two types of circulatory systems echinoderms have

• Has a water vascular system and a haemal system 

  • Water vascular system

    • Gas exchange

    • Excretion of wastes

    • Feeding

    • Locomotion

    • Circulates seawater through a series of canals 

  • Haemal system

    • Moving nutrients and wastes 

    • Circulates a body fluid with nutrients but lacks a respiratory system 

Open Circulatory System

Present in Arthropoda, Mollusca (bivalves and gastropods). Controlled by a neurogenic heart. Bodies are filled with hemolymph

• Pros:

  • Less energy needed to move fluids

  • Fewer structural elements

  • Better temperature regulation

• Cons:

  • Slower with non-targeted oxygen delivery (cannot vasodilate/constrict)

  • Unsuitable for larger organisms and/or those with higher metabolic rates 

Hemolymph

Water with ions, nutrients, hormones, hemocytes (immune cells), and maybe some  oxygen-carrying pigments (which are not enclosed in a “red blood cell”...so...it’s not blood).

Neurogenic Heart

Heart pumping is controlled by nerve signals from the brain 

Closed Circulatory Sytem

Present in Annelida, Vertebrata, Mollusca (cephalopods). Fluids entirely contained within vessels. Closed systems have a myogenic heart

Arteries

• moves blood away from the heart

• Thicker muscle & elastin layer = stretchy and strong so as not to burst with a big gush of blood from the heart

• No valves

Veins

• blood is returning to the heart

• Thinner muscle & elastin layer 

• Valves = prevent backflow of blood

Capillaries

Location of material exchange with other tissues. Gas exchange nutrients move into tissues, waste moves out of tissues

Single Circuit

• Heart -> Gills -> Body -> Heart

• Blood flows through the heart only once in each complete circuit of the body

• Two pumping chambers with four total chambers involved. 

• Primarily present in fish

Double Circuit

• Heart -> Lungs -> Heart -> Body -> Heart

• Two separate pathways for blood!

  • Systemic Circuit = to the body

  • Pulmonary Circuit = to the lungs

• Can have two or three chambers 

  • Three chambers are found in most reptiles and amphibians

  • Four chambers are found in mammals, birds, crocodilians

Heart pumping steps

1. Blood ENTERS the heart into Atria

2. Blood always moves from Atria to Ventricles

3. Blood leaves the heart from ventricles and goes into the lungs

4. Blood from the lungs returns to the heart via the atria.

Ventricle

One of the two lower pumping chambers of the heart that pumps to the lungs

Atria

One of the two upper receiving chambers of the heart, receives blood from lungs.

Gap Junctions

• channels that allow direct passage of ions between cells = fast electrical communication.

Intercalated Discs

• where cardiomyocytes are structurally joined. Mechanically, these connections prevent cells from separating during heart contractions! 

Large intestine

The section of the digestive tract that absorbs water and electrolytes and houses

fermentative bacteria.

Small intestine

The section of the digestive tract where most enzymatic digestion and nutrient absorption

occur.

Synapomorphy

A derived trait shared by a group of organisms and their most recent common ancestor,

used to define a clade.