Introduction

• Exchange and transport in animals are essential processes that ensure the proper functioning of their bodies.

• These processes involve the movement of gasses, nutrients, and waste products within an organism.

Respiratory System

• It is mainly done through gas exchange, Animals need to exchange gases, primarily oxygen and carbon dioxide, with their environment.

• Here we have two kinds of animals, the Terrestrial and Aquatic Animals which use specialized respiratory organs or structures in order to breathe.

Terrestrial Animals

• Terrestrial animals live on land. For them, the source of oxygen is the atmosphere. The oxygen is released by the green plants during the process of photosynthesis. 

• Terrestrial animals use respiratory systems made of lungs that are connected to the external environment via nasal chambers or openings. 

• They inhale the oxygen along with other gasses and exchange the oxygen with blood in the lungs. In this process, the carbon dioxide is expelled out.

• Air contains more O2 as compared to water. Since the content of O2 in the air is high, the terrestrial animals do not have to breathe faster to get more oxygen. 

• Therefore, they do not need adaptations for gaseous exchange and can adapt to a relaxed mode of breathing.

Aquatic Animals

• Aquatic animals live in water. So accordingly, they have modified their bodies to suit the aquatic habitat.

• Unlike terrestrial animals, the aquatic animals are of different types. 

• The unicellular organisms like Amoeba simply use the cellular surface for diffusion of gasses, that intake of oxygen and giving out carbon dioxide. 

• Animals like fish and frogs use the gills for extracting the oxygen from the water. The gills are heavily supplied with blood capillaries. 

• As the water passes through the gills, the oxygen is filtered and absorbed in the blood.

• These animals are mainly involved with water, we know that water is composed of two molecules of hydrogen and one molecule of oxygen.

• So we say that the oxygen is dissolved in water. 

• They need to use the oxygen dissolved in water. Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.

Circulatory System

• The circulatory system is the link between all the cells of the body and these exchange systems. 

• It consists of the heart, blood and blood vessels, and facilitates the transport of gasses, nutrients, and waste products throughout the body.

• Here we have two types, the Open and Closed Circulatory System.

• Since animals are of various types they need to have a specialized structure or process in order to make transportation of gasses, nutrients and waste products throughout the body possible.

Open Circulatory System

• It is primarily found in invertebrates. Here, the blood flows freely through cavities since there are no vessels to conduct the blood.

• It happens when there are no vessels to contain the blood, and it flows freely through the cavities of the body.

Closed Circulatory System

• It is found in vertebrates and a few invertebrates, like earthworms. 

• This system has vessels that conduct blood throughout the body. 

• Blood can flow through vessels inside the body, such as arteries and veins.

Digestive System

• The digestive system is responsible for breaking down complex nutrients into simpler forms that can be absorbed. 

• Nutrients are then transported through the circulatory system to cells for energy and growth.

• The structure and function of the digestive system in animals are highly influenced by their dietary habits, lifestyles, and evolutionary adaptations. 

• Different animal species have evolved specific digestive strategies to efficiently extract nutrients from the available food sources. 

Here are some examples of how digestive systems vary among different groups of animals:

Herbivores

Characteristics: Herbivores primarily consume plant material.

Adaptations:

• Specialized Teeth: Often have flat molars for grinding plant material.

• Long Digestive Tracts: Herbivores typically have longer digestive tracts to allow for the extended breakdown of cellulose, a complex carbohydrate found in plant cell walls.

• Fermentation Chambers: Some herbivores, like ruminants (cows, sheep), have multiple stomach compartments for the fermentation of cellulose by symbiotic microbes.

Carnivores

Characteristics: Carnivores primarily consume animal flesh.

Adaptations:

• Sharp Teeth: Carnivores have pointed teeth for tearing and shredding meat.

• Shorter Digestive Tract: Carnivores often have a shorter digestive tract because animal proteins are easier to digest compared to plant material.

• Stomach Acidity: Increased stomach acidity helps in the breakdown of proteins and sterilizes ingested meat.

Omnivores

Characteristics: Omnivores consume both plant and animal material.

Adaptations:

• Variable Dentition: Omnivores may have a combination of sharp and flat teeth to handle a diverse diet.

• Moderate Digestive Tract Length: The digestive tract is adapted to handle a range of food types, with characteristics falling between those of herbivores and carnivores.

Insectivores

Characteristics: Insectivores primarily feed on insects and other invertebrates.

Adaptations:

• Specialized Teeth: Adapted for capturing and consuming insects.

• Simple Stomachs: The digestive system is often relatively simple, reflecting the nutritional content and digestibility of insects.

Frugivores

Characteristics: Frugivores primarily consume fruits.

Adaptations:

• Specialized Teeth: Adapted for biting into and consuming fruits.

• Short Digestive Tract: Fruits are relatively easy to digest, and a shorter digestive tract is often sufficient.

Filter Feeders

Characteristics: Filter feeders consume small particles from the surrounding environment.

Adaptations:

• Filtering Structures: Specialized structures (e.g., baleen plates in baleen whales) for filtering small organisms from water.

Excretory System

• Animals excrete urine and waste products through specialized structures and organs within their excretory systems. 

• The process of excretion involves the removal of metabolic waste products from the body to maintain internal balance and homeostasis. Different animal groups have evolved various mechanisms for excretion.

• The specific mechanisms of excretion can vary widely among different animal groups, reflecting adaptations to their environments and lifestyles.         

Here we have various types of animals and their ways on how they excrete waste products:

Vertebrates (e.g., Mammals, Birds, Reptiles)

• Organs: The primary excretory organs in vertebrates are the kidneys.

• Urine Formation: Blood is filtered in the kidneys, where waste products, excess salts, and water are removed to form urine.

• Storage: The urine is then transported from the kidneys to the bladder for temporary storage.

• Elimination: When the bladder is full, urine is expelled from the body through the urethra during the process of micturition.

Insects

• Organs: Insects have specialized structures called Malpighian tubules.

• Urine Formation: Hemolymph (the insect's circulatory fluid) is filtered through Malpighian tubules, and waste products, including nitrogenous compounds, are excreted as a concentrated solution.

• Storage and Elimination: The concentrated waste solution is then transported to the hindgut, where water and useful substances are reabsorbed. The remaining concentrated waste is eliminated from the body as feces.

Fish

• Organs: Fish have kidneys, similar to those in vertebrates.

• Urine Formation: Filtration and urine formation occur in the kidneys, where nitrogenous waste, salts, and water are removed from the blood.

• Elimination: The urine is expelled through the urinary duct into the cloaca, a common chamber for the release of urine and reproductive products.

Birds

• Organs: Birds have paired kidneys.

• Urine Formation: Birds excrete nitrogenous waste in the form of uric acid, which is less toxic and conserves water. The urine is formed in the kidneys.

• Elimination: Uric acid, along with some water, is excreted through the cloaca. Birds do not have a separate bladder for urine storage.

Flatworms (e.g., Planarians)

• Organs: Flatworms possess a simple excretory system called protonephridia.

• Urine Formation: Protonephridia remove excess water and waste products through specialized flame cells. The waste is expelled through excretory pores.

• Elimination: The waste is eliminated directly through excretory pores on the body surface.