Comprised Bio Exam 3

What type of organic molecules must animals obtain from food?

Carbohydrates, proteins, lipids, nucleic acids, vitamins, and minerals

Why must animals eat essential nutrients?

They cannot synthesize them internally and must obtain them from food

What are essential nutrients?

Nutrients an animal cannot make itself

Where are essential amino acids synthesized?

In plants

Why do animals need energy?

Growth, tissue maintenance, movement, and heat production

What is metabolic rate?

The amount of energy used per unit in time

What is BMR (Basal Metabolic Rate)?

Metabolic rate at rest

How is metabolic rate measured?

By oxygen consumption ( = heat production)

What happens to energy from food?

Chemical bonds break making ATP and heat

How does exercise affect metabolic rate?

Increases metabolic rate

How does body size affect metabolic rate?

Smaller animals have higher metabolic rate per gram

What is predation?

Eating other animals

What is herbivory?

Eating plants

What is suspension feeding?

Eating small particles suspended in water

What is symbiosis in feeding?

Obtaining food from microbial partners

What is a fluid feeder?

Consumes liquid nutrients

What is a suspension feeder?

Filters small organisms from water

What is a deposit feeder?

Eats particles from sediment (e.g., earthworms)

What is bulk feeding?

Eating large pieces or whole organisms

What are carbohydrates used for?

Energy and storage

What are proteins used for?

Structure and function (enzymes)

What are lipids used for?

Energy storage and membranes

What is calcium used for?

Bones, nervous system, muscle fucntion

What is phosphorus used for?

ATP, nucleic acids, bones

What is division of labor?

Cells specialize for specific functions

What is a tissue?

Group of similar cells

What is an organ?

Structure with multiple tissue types

Why is a circulatory system important?

It transports nutrients to specialized tissues

What is epithelium?

A thin layer of cells lining surfaces and organs

Why is the digestive epithelium thin?

Allows efficient absorption

What is peristalsis?

Muscle contractions that move food through the tract

What happens in the midgut?

Continued digestion + enzyme and bile action

Where does most absorption occur?

Later part of the midgut

What is the brush border?

Surface area of intestinal cells that aids in absorption

How are nutrients transported after absorption?

Via the circulatory system

How does diet affect digestive tract length?

Herbivores → long intestines

Carnivores → shorter intestines

Why do herbivores have longer intestines?

To digest plant material (cellulose)

What is a gizzard?

Structure that uses stones to grind food (birds)

What are mandibles?

Arthropod mouthparts for chewing

What is a crop?

Storage chamber for food

Why can’t vertebrates digest cellulose alone?

They lack necessary enzymes

How do herbivores digest cellulose?

Through symbiotic microbes

Why do smaller animals need more food per gram?

Higher metabolic rates

What is the mouse-to-elephant curve?

Shows inverse relationship between body size and metabolic rate per gram

How do other systems support digestion?

Sensory → detect food

Skeletal → teeth

Muscular → chewing & movement

Excretory → waste removal

What are the three basic functions of the nervous system?

Sensory input, integration, and motor output

What is sensory input?

Detection of stimuli by receptors

What is integration?

Processing information (thoughts, memory, decisions)

What is motor output?

Response via effector organs (muscles/glands)

What are the main parts of a neuron?

Cell body (soma), dendrites, axon, and axon terminals

Function of dendrites

Receive incoming signals

Function of axon

Conduct electrical signals away from the cell body

Function of axon terminals

Release neurotransmitters

What is membrane potential?

Electrical potential difference across a cell membrane

What creates membrane potential?

Separation of ions across the membrane

What is voltage?

Stored potential energy from separated charges

What is current?

Flow of charged particles

What is the resting membrane potential?

The stable negative charge inside a neuron ( ~ -70 mV)

How is the resting membrane potential established?

Na+/K+ pump (3 Na+ out, 2 K+ in)

K+ leak channels

Unequal ion distribution

Which ion is most important for resting potential?

K+

What are gated channels?

Channels that open in response to stimuli

Types of gated channels

Ligand-gated

Voltage-gated

What is a graded potential?

Small, local change in membrane potential

Characteristics of graded potentials

Variable strength

Short distance

Can be excitatory or inhibitory

What is summation?

Addition of multiple graded potentials at the trigger zone

What is an action potential?

A rapid, long-distance electrical signal

Key properties of action potentials

All-or-nothing

Does not decrease with distance

What is depolarization?

Na+ channels open

Na+ rushes in

Membrane becomes positive (~ +30 mV)

What is repolarization?

Na+ channels inactivate

K+ channels open

K+ exits cell

What is hyperpolarization?

K+ channels stay open too long

Membrane becomes more negative than resting

How is resting potential restored?

Na+/K+ pump resets ion gradients

What is threshold?

Minimum depolarization needed to trigger an action potential

What happens if threshold is reached?

Voltage-gated Na+ channels open → full action potential

What is propagation?

Movement of the action potential along the axon

Why doesn’t the signal weaken?

Continuous regeneration via voltage-gated channels

What is myelin?

Insulating layer around axons

What does myelin do?

Prevents ion leakage

Increases conduction speed

What is saltatory conduction?

Action potentials “jump” between nodes → faster transmission

What is a synapse?

Junction between neurons

What happens at a chemical synapse?

neurotransmitter released

Binds to receptors on postsynaptic cell

What are the two possible effects at a synapse?

Depolarization (excitation)

Hyperpolarization (inhibition)

Why are neurons said to “integrate” signals?

They combine multiple inputs (excitatory + inhibitory) before firing

What is the main function of sensory systems?

To gather information about internal and external environments so animals can function successfully

What does it mean that “sensory receptor cells transform stimuli into electrical signals”?

They convert environmental energy (light, sound, chemicals, etc.) into electrical signals the nervous system can process

What is transduction?

The conversion of energy from one form (stimulus) into electrical signals

What is the first step in receptor cell signaling?

Graded potentials (strength increases with stronger stimulus)

What is the second step in receptor cell signaling?

Action potentials generated in neurons

Where are sensory signals sent after transmission?

To integrative parts of the nervous system (brain, spinal cord, ganglia)

Why do receptor cells have large membrane surface areas?

To increase sensitivity and allow more receptor proteins

What are the two types of receptor proteins?

Ionotropic and metabotropic

What is an ionotropic receptor?

A receptor that is also an ion channel

What is a metabotropic receptor?

A receptor that uses G-proteins and second messengers to affect ion channels

How does the brain distinguish different sensory signals?

Signals are sent to specific processing regions (labeled line coding)

What is labeled line coding?

Specific neurons carry specific types of sensory information to specific brain regions

What type of receptors are used in olfaction?

Metabotropic receptors

What are odorants?

Chemical molecules detected by smell

Where are olfactory receptors located?

In the olfactory epithelium in the nasal cavity

Why can animals detect many different smells?

They have many different G-protein-coupled receptors (GPCRs)

What is special about olfactory receptor cells?

Each cell expresses only one type of receptor

What are photoreceptors

Cells that detect light