Amphibians and Terrestrial Animals Quiz

Terrestrial Animals

• Animals originated in the oceans
• Land-dwelling animals evolved from ancestors that independently left aquatic environments
• The earliest recorded terrestrial animal was a myriapod, 428 million years ago, but the first transition likely occurred earlier
• Relatively few terrestrial animal taxa exist, including gastropods, arthropods (insects, arachnids, myriapods, crustaceans), nematodes, annelids, and amniote vertebrates.
• Terrestrial environments have provided many evolutionary opportunities for these taxa.

Conditions on Land

• Gravity affects posture and locomotion
• Air is a less dense medium than water, presenting challenges for obtaining oxygen
• Locomotion, sensory modes, and thermal properties differ between aquatic and terrestrial environments.
• Water remains a limiting resource in terrestrial habitats.
• Sunlight exposure to UV radiation is greater in air than water.

Life on Land

• Desiccation avoidance is a key challenge for terrestrial life
• Mechanisms for reducing water loss and replacing lost water are crucial for survival
• Desiccation tolerance methods, like aestivation and life cycles, are employed by some animals
• Excretion requires adjustments to maintain water balance
• Gas exchange in air requires specialized internalized organs like lungs, book lungs, or tracheal systems to avoid water loss.

Desiccation and the Environment - Terrestrial Animals

• Terrestrial animals are constrained by water availability
• Animal anatomy, behavior, and physiology are uniquely adapted to varying levels of water availability.

Nitrogenous Wastes

• Toxic ammonia (NH₃) is produced in every cell of the body from the catabolism of amino acids and nucleic acids
• Reptiles, birds, and insects convert ammonia into uric acid, a semi-solid, low water-solubility waste, allowing for water conservation during excretion.

Desiccation and The Environment - Mammals

• Mammals are ureotelic, converting ammonia to the less toxic urea in order to minimize water loss in excretion
• The loop of Henle aids in the conservation of water, producing highly concentrated urine, which is hyperosmotic to blood.

Desiccation and The Environment - Insects

• Insects deal with low body size, evaporation, and water loss from their respiratory systems
• Minimizing water loss is crucial; waxy cuticles and spiracles help regulate water loss.

Desiccation Tolerance

• Tardigrades can enter a cryptobiotic or anhydrobiotic state in response to environmental stressors, allowing them to survive harsh conditions
• Rotifers exhibit a similar response, forming a desiccation-resistant zygote when facing environmental extremes.

Aestivation

• Aestivation involves decreasing metabolism to conserve water.
• Desert spadefoot toads and some desert-dwelling frogs exhibit aestivation as an adaptation to drought conditions

More Requirements for Terrestrial Life

• Protection of gametes and embryos from desiccation (internal fertilization, thick egg coverings)
• Adaptations to cope with temperature extremes, including thermoregulation for maintaining an optimal body temperature
• Adaptations to constraints on sensory systems, such as using specialized chemosensors or mechanosensors.
• Mechanisms for supporting body weight through robust skeletons and appropriate size/volume relationships.

The Senses in Air and Water

• Air transmits light more efficiently than water, so vision in air can be improved
• Water conducts sound more effectively than air
• Different senses have evolved to detect and process information more efficiently based on their respective mediums (liquid or gas).

Chemosensors

• Chemosensory organs require a moist surface for the absorption of airborne chemical particles
• Insect antennae have minute channels lined with moist, adsorptive tissues
• Terrestrial vertebrates have moist olfactory epithelium and taste buds in the oral cavity.

Hearing

• Sound does not transmit easily between air and water, so specialized structures have evolved in terrestrial animals to detect and respond to air-borne sound
• Insects also have specialized auditory structures allowing them to sense vibrations in the air
• Vertebrates use the middle ear bones to convert sound vibrations for fluid translation in the cochlea.

Hearing and Balance

• Vertebrates have vestibular labyrinths that provide information about their position and directional orientation.
• The inner ear helps detect and interprets sounds for a range of applications, including position, balance, and movement.

Support Body Weight

• The volume (mass) of terrestrial organisms grows proportionally faster than their limb cross-sectional support area.
• Limbs must develop disproportionately to effectively support increasing body weight and size
• Aquatic animals do not face this constraint because water supports their body mass via neutral buoyancy.

Allometry

• Allometry describes the varying growth rates of different body parts, which change proportional to the overall body size.

Hard Skeletons

• Skeletons exist in both aquatic and terrestrial animals in the forms of endoskeletons (inside the body) and exoskeletons (covering the body).
• They transmit forces, provide body support and structural framework, and act as a bank for physiological requirements.

Endoskeletons

• Vertebrate endoskeletons are composed of bone and cartilage that provide structural support and transmission of stress throughout the body
• Bone tissue is largely vascularized and metabolically active, creating a resilient support system resistant to compressing forces.

Exoskeletons

• Arthropods possess exoskeletons composed of chitin and often impregnated with calcium carbonate.
• These segmented plates, connected by joints between them, allow for mobility and support body segmentation

Hydrostatic Skeletons

• Hydrostatic skeletons typically consist of fluid-filled compartments within soft-bodied animals.
• Contractions of muscles in the surrounding layers change the shape of the fluid-filled compartments. This creates support needed for movement, support, and flexibility.

Aquatic Animals

• Water supports the animal's body, which influences its size, posture, and skeleton
• Desiccation is a negligible concern in aquatic environments.
• Stable environments often have consistent temperatures, minimal temperature extremes
• Metabolic waste is easily removed via water.
• Sound transmission is most effective from water to the organism's body.

Challenges of Living in Aquatic Environments

• Water's density and viscosity present challenges for movement, and energy expenditure.
• Oxygen levels in water are often lower than in the air.
• Water's thermal conductivity is much higher, creating different thermal balance needs.

Endoskeletons - Terrestrial vs. Aquatic

• Terrestrial animals have heavily enclosed ribcages and other girdles for support
• Aquatic animals feature more loosely attached structures due to water's support.

Aquatic Animals Growth

• Aquatic animals can significantly exceed terrestrial animal sizes due to the supporting effects of water's buoyancy
• The size limitations for terrestrial animals imposed by weight constraints do not apply to aquatic animals to the same extent

Salt and Water Balance

• Marine vertebrates need adaptations to expel excess salt acquired through their environment
• Salt glands, located near the upper respiratory tract or eyes, excrete salt.

Being Warm in Aquatic Environments

• Water is a good heat conductor, and aquatic organisms are mostly ectothermic
• Aquatic homeothermic endotherms must insulate with blubber or pelage

Insulation in Aquatic Environments

• Insulation, such as blubber or fur, allows heat retention
• Respiratory mediums such as air also assist in metabolic activity, allowing for greater thermal regulation capacity
• Heat exchange via concurrent systems, in which cooled arteries warm incoming blood, supports thermal regulation

Torpor and Hibernation

• Torpor is a metabolic state characterized by a decrease in metabolic rate and body temperature
• Hibernation, a seasonal form of torpor, is employed as an adaptation to low temperature conditions.

Endothermy in Insects

• Some insects exhibit endothermy, generating heat through the action of their flight muscles, which are used for warming up for flight activity and maintaining higher thorax temperatures.

Freeze Tolerance and Freeze Avoidance

• Freeze avoidance is used by some ectothermic aquatic animals; they can supercool but avoid freezing
• Freeze tolerance is employed by some terrestrial ectotherms; they endure freezing in their extracellular fluids.

Summary of Terrestrial vs. Aquatic Differences

• Terrestrials face challenges with desiccation and support, while aquatics deal with low oxygen, high water density.
• Both have specific constraints and requirements.

Test your knowledge on amphibian reproduction, egg characteristics, and the adaptations of terrestrial animals for survival. This quiz covers topics related to temperature regulation, limb growth, and structural requirements in different environments. Perfect for biology students exploring vertebrate physiology.