MOVEMENT
GRADE 11 BIOLOGY
Movement refers to the act or process of changing physical position or location. It is a
fundamental aspect of life and is observed in various forms across the animal and plant
kingdoms.
In the context of organisms, movement enables them to interact with their environment, seek
resources, escape predators, and engage in various behaviors necessary for survival and
reproduction. Organisms exhibit different types of movement, such as walking, running,
swimming, flying, crawling, or even jumping, depending on their anatomical structure and
evolutionary adaptations.
Movement is made possible through the coordination of various physiological systems and
structures, including muscles, bones, joints, nerves, and sensory organs. Muscles generate the
necessary force to produce movement, while the skeletal system provides support and acts as a
framework for the body.
Growth movement and locomotory movement are two distinct types of movement observed in
living organisms.
Growth movement, also known as tropism, refers to the directed movement of a plant or plant
part in response to an external stimulus, such as light, gravity, or touch. These movements are
typically slow and occur over an extended period. Growth movement allows plants to optimize
their growth and development by adjusting their orientation or position in relation to
environmental cues. Three common examples of growth movement include.
● Phototropism: The bending of a plant stem towards a light source.
● Gravitropism (Geotropism): The response of roots growing downwards towards gravity
and shoots growing upwards against gravity.
● Thigmotropism: The response of plant tendrils or climbing plants to touch, allowing
them to grip and support themselves.
A germinating seedling displays growth movements known as positive phototropism and
negative gravitropism as it emerges from the soil and reaches towards the light.
Positive Phototropism: Phototropism is the growth movement of plants in response to light. In
the case of a germinating seedling, the shoot (stem) exhibits positive phototropism by bending or
curving towards a light source. This movement is crucial for the seedling to optimize its
exposure to light, which is necessary for photosynthesis and the production of energy.
When a seed germinates underground, the shoot tip (also called the apical meristem) starts
elongating and pushing through the soil. Once it emerges into the air, it senses the direction of
light. Cells on the shaded side of the shoot elongate more rapidly than those on the illuminated
side. This differential growth causes the shoot to bend towards the light source, allowing the
leaves to receive maximum light for photosynthesis.
Negative Gravitropism: Gravitropism, also known as geotropism, is the growth movement of
plants in response to gravity. In the case of a germinating seedling, the roots exhibit negative
gravitropism, which means they grow in the opposite direction of gravity, downwards into the
soil.
When the seed germinates, the root tip (also called the radicle) emerges and grows in the
direction away from the light, towards the force of gravity. This downward growth is essential
for the roots to anchor the seedling in the soil and to uptake water and nutrients.
These movements are typically mediated by differential growth rates or hormone distribution
within the plant, resulting in curvature or bending towards or away from the stimulus.
The negative gravitropic response in roots is regulated by specialized cells called statocytes,
which contain dense starch grains known as statoliths. These statoliths settle under the influence
of gravity and trigger signaling pathways that result in the asymmetric distribution of auxin
hormone. This asymmetry leads to differential cell elongation, causing the roots to grow
downward.
Locomotory movement refers to the self-propelled movement of an organism from one place to
another. It is associated with the displacement of the entire organism or specific body parts.
Locomotory movement is commonly observed in animals and is essential for various purposes
such as foraging, escaping predators, finding mates, and exploring new habitats. Examples of
locomotor movements include:
● Walking and running in terrestrial animals.
● Swimming in aquatic animals, which could involve undulating movements of the body or
the use of fins or flippers.
● Flying in birds, bats, and insects, achieved through the flapping of wings or gliding.
Importance of Locomotion
Locomotion is a crucial process in the animal kingdom. Some reasons include:
★ Survival and Predation: Locomotion enables animals to search for food, water, and
shelter, helping them meet their basic survival needs. It allows them to actively seek out
resources and escape from unfavorable conditions. Animals that are capable of effective
locomotion have an advantage in finding prey or evading predators.
★ Feeding and Foraging: Locomotion allows animals to reach food sources and acquire
nutrition. It enables them to move towards plants, other organisms, or carcasses to obtain
sustenance. Foraging behavior often involves searching, exploring, and traveling to find
food, a process facilitated by locomotion.
★ Reproduction and Mate Selection: Locomotion plays a crucial role in animal mating
behaviors. It allows individuals to seek out potential mates, engage in courtship rituals,
and compete for access to breeding partners. Locomotion also enables animals to disperse
and find suitable habitats for reproduction and rearing offspring.
★ Migration and Dispersal: Many animals undertake long-distance migrations to reach
breeding grounds, find better food sources, or avoid harsh environmental conditions.
Locomotion is essential for animals to navigate over long distances and successfully
complete these migratory journeys. Similarly, locomotion facilitates the dispersal of
offspring to new areas, reducing competition and promoting genetic diversity.
★ Exploration and Adaptation: Locomotion enables animals to explore their
environment, discover new resources, and adapt to changing conditions. Animals that can
move efficiently and explore different habitats have a greater chance of finding suitable
niches and adapting to ecological changes.
★ Social Interactions: Locomotion allows animals to interact with conspecifics (members
of the same species) and other individuals in their environment. It facilitates social
behaviors such as group formation, territorial defense, communication, and cooperation.
Animals that can move effectively can establish and maintain social relationships,
enhancing their reproductive success and survival.
LOCOMOTOR SYSTEM IN HUMANS
The locomotor system in humans, also referred to as the skeletal or musculoskeletal system, is
a complex system that enables movement, support, and stability of the body. It is made up of
various components, including bones, joints, muscles, tendons, ligaments, and connective
tissues, all working together to facilitate locomotion.
Bones: The skeletal system provides the framework and support for the body. It consists of
bones, which are hard, mineralized structures that form the skeleton. Bones serve multiple
functions, including providing structural support, protecting vital organs, producing blood cells,
and acting as storage sites for minerals like calcium.
Joints: Joints are the connections between bones. They allow movement and flexibility while
providing stability. Different types of joints exist, such as hinge joints (e.g., elbow and knee
joints), ball-and-socket joints (e.g., shoulder and hip joints), and pivot joints (e.g., the joint
between the first two cervical vertebrae). Joints are supported by ligaments, which are strong
bands of connective tissue that hold bones together.
Muscles: Muscles are soft tissues that contract and relax to generate force and produce
movement. They are responsible for the voluntary movements of the body. Muscles are
categorized into three types: skeletal muscles, smooth muscles, and cardiac muscles. Skeletal
muscles are attached to bones via tendons and are under conscious control. They work in pairs or
groups to produce coordinated movements across joints.
Ligaments: Ligaments are strong, elastic bands of connective tissue that connect bones to other
bones, providing stability and limiting excessive movement at joints. Ligaments help maintain
the integrity of joints and prevent dislocation or excessive strain.
Connective Tissues: In addition to tendons and ligaments, various other connective tissues, such
as cartilage and fascia, are present in the locomotor system. Cartilage provides cushioning and
support in joints, reducing friction and absorbing shock. Fascia is a connective tissue that
encloses and separates muscle groups, providing structural organization and support.
It is important to note that the nervous system plays a vital role in controlling and coordinating
the functions of the locomotor system. Nerves transmit signals from the brain to the muscles,
enabling voluntary movement, while also providing feedback regarding the position, balance,
and coordination of the body.
The human skeletal system serves different purposes. These include:
● Support: The skeletal system provides a structural framework that supports the body. It
gives the body its shape and rigidity, allowing us to stand upright and maintain posture.
● Protection: The bones of the skeletal system protect vital organs and delicate tissues. For
example, the skull protects the brain, the ribcage safeguards the heart and lungs, and the
vertebrae shield the spinal cord.
● Movement: The bones, along with the associated muscles and joints, enable movement.
Muscles attach to bones via tendons, and when they contract, they pull on the bones,
causing movement at the joints. The skeletal system acts as a lever system, allowing us to
perform various movements, from simple actions like walking to complex activities like
dancing or playing sports.
● Blood Cell Production: The bone marrow, found within certain bones, is responsible for
the production of blood cells. Red blood cells, white blood cells, and platelets are formed
in the bone marrow and play crucial roles in oxygen transport, immune function, and
blood clotting, respectively.
● Mineral Storage: Bones act as a reservoir for minerals such as calcium and phosphorus.
These minerals can be released from bones into the bloodstream as needed to maintain
mineral balance in the body. Calcium, in particular, plays a critical role in various
physiological processes, including muscle contraction, nerve function, and blood clotting.
● Movement and Support for Soft Tissues: The skeletal system provides attachment
points for muscles, tendons, and ligaments. Muscles attach to bones via tendons, allowing
them to exert force and generate movement. Ligaments connect bones to other bones at
joints, providing stability and limiting excessive movement.
The human skeletal system consists of approximately 206 bones, which are classified into two
main types:
➔ Axial Skeleton: The axial skeleton includes the bones that form the central axis of the
body. It consists of the skull, vertebral column (spine), and the ribcage (ribs and
sternum). The axial skeleton protects vital organs such as the brain, spinal cord, and
heart.
➔ Appendicular Skeleton: The appendicular skeleton includes the bones of the limbs
(arms and legs) and their associated girdles (shoulder and pelvic girdles). The
appendicular skeleton is involved in movement and locomotion.
MOVEMENT MECHANISM IN A HUMAN FORELIMB
The movement mechanism in the forelimb of a human primarily involves the coordinated action
of bones, joints, muscles, tendons, and ligaments. The forelimb, which includes the arm,
forearm, wrist, and hand, allows humans to perform a wide range of complex movements and
manipulations.
The relationship between bones and muscles in a limb is essential for movement and locomotion.
Bones provide a rigid framework, while muscles generate the force necessary to move the bones.
Attachment: Muscles are connected to bones through tendons. Tendons are tough, fibrous
connective tissues that attach muscle to bone. Tendons transmit the force generated by muscle
contractions to the bones, allowing movement.
Joint Movement: Muscles span joints and cross them, with tendons attaching on either side of
the joint. When a muscle contracts, it pulls on the tendon, which, in turn, pulls on the bone,
causing movement at the joint. The joint acts as a fulcrum, enabling the lever-like action of the
limb.
Agonist and Antagonist Muscles: The movement of a limb typically involves the coordinated
action of agonist and antagonist muscles. Agonist muscles are responsible for initiating and
producing a specific movement, while antagonist muscles oppose or reverse the action of the
agonist muscles. For example, when you flex your arm, the biceps brachii acts as the agonist
muscle, contracting to bend the elbow, while the triceps brachii serves as the antagonist muscle,
relaxing to allow the movement. The interaction between agonist and antagonist muscles enables
controlled and coordinated movement.
Muscle Fiber Arrangement: The arrangement of muscle fibers within a muscle affects the
force and direction of movement. Muscles can have different fiber arrangements, such as
parallel, pennate, or circular. Parallel muscles, like the biceps, have fibers that run parallel to the
long axis of the muscle and produce a large range of movement but generate less force. Pennate
muscles, such as the deltoid, have fibers that are obliquely arranged, allowing them to generate
more force but with a smaller range of movement. Circular muscles, like the orbicularis in the
eye, form rings around body openings and function in constriction or dilation.
Muscle Contraction and Relaxation: Muscles contract and relax to generate force and produce
movement. When a muscle receives a signal from the nervous system, it undergoes a series of
biochemical reactions that result in the sliding of actin and myosin filaments within muscle
fibers, shortening the muscle and producing force. This process is known as muscle contraction.
When the nervous system stops sending signals, the muscle relaxes, returning to its original
length.
The terms "insertion" and "origin" are used to describe the attachment points of muscles to
bones. The origin of a muscle refers to its attachment point on the bone that remains relatively
fixed or stationary during muscle contraction. It is typically the proximal attachment point,
meaning it is closer to the body's midline or core. The origin is usually the more stable
attachment point of the muscle, providing a stable base for muscle action. When a muscle
contracts, it pulls on the bone at its insertion point, causing movement around the joint. The
insertion of a muscle refers to its attachment point on the bone that moves when the muscle
contracts. It is typically the distal attachment point, meaning it is further away from the body's
midline or core. The insertion is the point where the muscle exerts its force and produces
movement. When the muscle contracts, it pulls on the bone at its insertion, resulting in the
desired movement of the limb or body part.
Understanding the origin and insertion of muscles is important because it provides information
about the muscle's function, the direction of its force, and the movement it produces when it
contracts. By knowing the origin and insertion points, healthcare professionals, anatomists, and
physical therapists can better understand and analyze muscle function, movement patterns, and
potential dysfunctions or injuries related to specific muscles.
STRUCTURE OF A LONG BONE