subject guide notes
B3.3.1—Adaptations for movement as a universal feature of living organisms
movement allows organisms to interact with their environment, obtain resources (such as finding shelter, or prey), find a mate, respond to threats, mark their territory, migrate, & engage in social behaviours
motile organisms - actively move from one place to another
ex: squids and octopuses release a stream of jet from a muscular tube. the tube can be directed in any way, propelling the organism forward and allowing it to move
sessile organisms cannot move, so they rely on the environment to provide them with food & resources
ex: the plant Mimosa pudica folds its leaves and drops its stem, in an effort to deter herbivores from consuming the plant
*note, barnacles are a “special” case because they engage in swimming behaviours that allow them to move, but then they stick to a hard surface once they’re older. but, they still hv appendages that allow them to obtain food. this technically doesn’t fit the criteria for sessile, as the barnacle doesn’t rely on the environment to provide it with food
B3.3.2—Sliding filament model of muscle contraction -COME BACK TO THIS
according to the theory, when a muscle is stimulated to contract, the actin filaments slide over the myosin filaments, towards the centre of the sarcomere
Z-discs are pulled closer together, shortening the sarcomere & the muscle fibre
the H & I bands are also shortened
B3.3.3—Role of the protein titin and antagonistic muscles in muscle relaxation
Titin: helps sarcomeres recoil after stretching & prevents overstretching
functions as a molecular spring
titin stretches as the sarcomere stretches, storing potential energy
provides passive resistance, preventing muscles from overstretching
*note, titin has a curvy shape, which means it is more flexible and can stretch efficiently
Antagonistic muscles: muscle tissue can only exert force when it contracts
B3.3.4—Structure and function of motor units in skeletal muscle
Structure of motor units: composed of a motor neuron, muscle fibres, and a neuromuscular junction
*note, neuromuscular junctions are present only in skeletal muscles
motor units are important for converting neural messages into movement,
B3.3.5—Roles of skeletons as anchorage for muscles and as levers
skeletons are a structural framework that’re composed of bone & other connective tissue
provide support and structure for organism, and serve as an anchorage point for muscles
Arthropods have exoskeletons
protect internal organs, functions as anchorage point for muscles & has to be regularly shed
Vertebrates have an endoskeleton
protects internal organs, functions as anchorage point
B3.3.6—Movement at a synovial joint
Bones - act as levers, and are an anchorage point for muscles
Synovial fluid - a lubricant between two bones in a synovial joint, and prevents them from rubbing against each other and producing friction
Ligaments - strong, flexible bands of connective tissue that connect bone to bone
Tendons - strong, fibrous bands of connective tissue that attach a muscle to the bone
Cartilage - covers the end of the bones and acts as a shock absorber. Also has a smooth surface, allowing the bones to easily move past each other
Muscles - bundles of fibres that produce movement when they contract
example of synovial joint - the hip joint
connects the femur bone in the thigh to the pelvis bone
is a ball-and-socket joint
knee, elbow and shoulder joint are also examples of synovial joints
B3.3.7—Range of motion of a joint
is the type & amount of movement that’s possible at that joint
joints with high ROM = wide range of movement
ex: hip & elbow joints
joints with low ROM = limited movement or no movement at all
ex: sutures in skull or vertebrae in spine
should be able to compare the range of motion using a goniometer or computer analysis
B3.3.8—Internal and external intercostal muscles as an example of antagonistic muscle action to facilitate internal body movements
External and internal intercostal muscles are an example of antagonistic muscle - the different orientation of these muscle fibres mean they move in opposite direction
when one layer contracts, the other layer is stretched & stores potential energy in titin
External intercostal muscles - most superficial, & when they contract, the rib cage is lifted up and out
Internal intercostal muscles - are deeper, and when they relax during inspiration, rib cage moves down & in
B3.3.9—Reasons for locomotion
Foraging - act of searching for & collecting food
can be in the form of hunting, grazing, searching & scavenging
ex: horses!!
they forage for around 16 hours a day
cover large distances each day in search of fresh vegetation, and will move from one location to the other
Escaping danger - organisms need to move quickly in order to avoid predation
ex: elephants
they can detect infrasonic sounds of tsunamis, before the tsunami hits the coast. this provides the elephants with enough time to flee to higher ground
Searching for a mate - animals that produce sexually, need to move to a location in order to find a mate
ex: pygmy three-toed sloth
travels & emits vocalization to alert potential mates of their location
some species also hv low population densities, such as territorial animals. due to external factors, these animals hv limited chances to mate
ex: tigers
tigers are a territorial animal, and due to habitat destruction & poaching, they hv limited chances to mate within their own territory. so, they have to travel longer distances to find a mate
Migration - the large-scale seasonal movement of an animal from one place to another
ex: Emperor Penguin
they migrate inland to their breeding grounds. when as egg has been laid, the female travels to the sea to feed, while the male incubates the egg. once the female returns after the egg has hatched, the female cares for the chick, and the male travels to feed
B3.3.10—Adaptations for swimming in marine mammals
Mammals are a group of endothermic animals that breathe air through lungs, give birth to live babies, produce milk to feed their young, and have hair or fur at some point in their lives
Streamlining - minimise drag, meaning the organism can easily move through water
marine mammals also typically hv a thick layer of blubber under their skin, which helps even their body shape & reduce drag. the layer of fat also helps insulate the mammal, and provide some buoyancy
Forelimbs forming flippers - they’re positioned on the sides of their bodies. are typically long & narrow, & can be used for steering and contribute to streamlined body
Tail to form a fat & wide fluke - the tail moves in a sweeping motion (up and down) which helps propel the organism forwards
Airway - there are changes to the airway which enable periodic breathing between dives
whales & dolphins hv a blowhole on their heads, which allow them to breathe without lifting their head out of the water
blow hole covered by muscular flap
when it’s contracted, it opens. when it’s relaxed, it covers & prevents the entry of water
are also used to communicate & convey info
these adaptions weren’t in the curriculum guide so idk if they help with swimming
Myoglobin - marine mammals hv a higher concentration of myoglobin in their muscle tissues
has a high affinity for oxygen, which allows marine mammals to store more oxygen & dive for longer periods of time
Larger lungs - hv larger lungs relative to their body size, as well as more capillaries surrounding their alveoli
allows them to take in more oxygen with each breath
higher volumes of blood - higher volumes of blood relative to their body size, which also allows them to carry more oxygen
also hv higher concentration of RBC’s in blood, and higher concentration of haemoglobin in their RBCs
this allows their bodies to contain & transport more oxygen
Large SA - minimizes their SA:V ratio, which minimizes the amount of heat lost to cooler ocean waters. this adaptation helps them maintain their body temp & conserve energy