Movement Underwater
Read Movement Underwater and check the IELTS Reading answers. Self-propelled motion is a fundamental ability in many organisms. From the beating flagella of tiny plankton keeping afloat near the ocean surface to the playful perfection of dolphins surfing the bow wave of a ship, marine creatures hav…
Passage preview
Self-propelled motion is a fundamental ability in many organisms. From the beating flagella of tiny plankton keeping afloat near the ocean surface to the playful perfection of dolphins surfing the bow wave of a ship, marine creatures have adopted a huge variety of styles, speeds, and methods of movement. Each species has its own particular need for the evolutionary developments that have taken place, but the basic requirements are the same-finding food, avoiding predation, seeking a mate or a safe place to have young, or migrating to an area with more favorable conditions.
Vocabulary from this passage
11 words worth learning before you sit the test, each with the sentence it appears in.
- drag resistance noun
The physical force that acts opposite to the relative motion of any object moving with respect to a surrounding fluid.
Marine animals have evolved streamlined body shapes specifically to minimize drag resistance and improve their swimming efficiency.
- formidable predator noun
An animal that hunts others and inspires fear or respect through being impressively powerful, large, or highly intense.
The barracuda is a formidable predator known for its lightning-fast acceleration when attacking unsuspecting prey.
- intricate adjective
Very complicated or detailed; consisting of many interconnecting parts that require careful navigation, observation, or detailed study.
Butterfly fishes navigate through the intricate structures of coral reefs with remarkable ease and precision.
- lubricate verb
To apply a substance to minimize friction and allow for smooth movement between surfaces or through a dense medium.
The scales of many fish are coated with a layer of slime to lubricate their passage through water.
- maneuverability noun
The ability of an object or organism to change direction or position with high levels of agility and precision.
Small reef-dwelling fish rely on their exceptional maneuverability to escape from larger predators in complex coral environments.
- neutral buoyancy noun
A condition where an object's average density is equal to the density of the fluid in which it is immersed.
Fish use their swim bladders to maintain neutral buoyancy, allowing them to stay at a specific depth effortlessly.
- scavenge verb
To search for and collect anything usable from discarded waste, or for animals to feed on dead animal carcasses.
Many slow-moving deep-sea fishes scavenge for food that falls from the nutrient-rich layers near the ocean surface.
- self-propelled adjective
Capable of moving on its own without external force, typically referring to organisms or complex mechanical systems.
Self-propelled motion is a fundamental ability that allows marine organisms to search for food and avoid predators.
- streamlined adjective
Having a design or form that presents very little resistance to a flow of air or water, increasing speed.
The torpedo-like shape of a tuna is a perfectly streamlined form that enables it to reach high speeds.
- undulation noun
A smooth, wavelike motion used by many aquatic animals for propulsion by moving the body in a rhythmic fashion.
Eels move through the water using a continuous undulation of their long, flexible bodies to generate forward thrust.
- viscous adjective
Having a thick, sticky consistency between a solid and a liquid; resistant to flow or movement through a medium.
Seawater is much more viscous than air, creating significant resistance for any creature moving through the ocean.
Answers with explanations
- 27. D
The question looks for a **strategy to avoid being attacked**. Paragraph D describes how plankton **sink back down in an effort to escape predators** at dawn, clearly outlining a specific defensive maneuver designed to avoid attacks.
- 28. C
The prompt asks about how fish **keep afloat naturally**. Paragraph C explains this internal biological mechanism, detailing that most fishes have **swim bladders to help them offset the density of their bodies and so maintain neutral buoyancy**.
- 29. G
The question asks for the **physical process** of forward propulsion. Paragraph G describes how strong muscles create curves that **press sideways and back against the water, producing a forward thrust**, which explains exactly how fish propel themselves.
- 30. A
The prompt searches for a **list of reasons** for movement. Paragraph A provides this exact list, stating the basic requirements include **finding food, avoiding predation, seeking a mate**, or migrating to favorable areas.
- 31. B
The question asks how water **restricts and aids movement**. Paragraph B notes that water causes **much more resistance to movement** (restricting) but adds that **with density comes much greater buoyancy**, allowing organisms to spend little energy staying afloat (aiding).
- 32. speed
The table requires the specialized ability of the Swordfish. The text states that the **tuna, swordfish, and mackerel all specialize in fast, steady cruising**, which relates directly to maintaining consistent **speed** over long distances.
- 33. acceleration
The table requires the specialized ability for the Barracuda. The text notes that this predator **specializes in swift acceleration**. The term 'acceleration' grammatically pairs with 'Rapid' in the table to correctly describe this burst-speed trait.
- 34. ["freshwater pike","pike"]
The table requires the name of the fish that executes a **sudden attack on prey** after waiting. The passage describes the **freshwater pike** as a fish that **lurks in the shadows until its quarry is within striking distance and then lunges**, making it the correct answer.
- 35. butterfly fishes
The table requires the name of the fish known for **rapid changes of direction**. The text explicitly links maneuverability to **butterfly fishes**, which have bodies that permit **abrupt changes of track**, matching the prompt exactly.
- 36. turbulent
The diagram blank requires an adjective describing the type of drag reduced by a tapered back. The text explicitly states that a tapered back end is required **To reduce the turbulent drag**. The word 'turbulent' fits perfectly.
- 37. up-and-down
The diagram asks for the type of movement controlled by pectoral and pelvic fins. The passage specifies that **up-and-down motion is controlled by the pectoral and pelvic fins**. The phrase 'up-and-down' acts as an adjective describing the movement.
- 38. sideways
The diagram requires the type of movement controlled by dorsal fins. The text explicitly mentions that **The vertically oriented dorsal and ventral fins on the back and belly control sideways motion**. The adjective 'sideways' fits the blank perfectly.
- 39. maneuverability
The diagram looks for a noun explaining the role of other fins. The passage states that the style and arrangement of these fins are **crucial for maneuverability**. This term properly identifies the overarching purpose of these fin adaptations.
- 40. form
The diagram blank asks for the type of drag reduced by minimal cross-sectional area. The text directly links these concepts, stating: **To reduce form drag, the cross-sectional area of the body should be minimal**. 'Form' is the correct descriptive noun.