Animal Kingdom

Animal Kingdom

High School

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Learning Objectives

• Describe the main characteristics that define the Animal Kingdom.

• Explain the primary differences between invertebrates and vertebrates.

• Compare the major phyla of invertebrates found in the animal kingdom.

• Distinguish between the major classes of animals within the vertebrate group.

Key Vocabulary

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Bilateral Symmetry

A body plan where a single line divides the organism into two mirror-image halves.

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Invertebrate

An animal that does not have a backbone, making up about 97% of all animal species.

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Vertebrate

An animal that possesses an internal skeleton with a backbone made of small pieces called vertebrae.

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Ectotherm

A cold-blooded animal whose body temperature changes to match its surrounding environment.

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Endotherm

A warm-blooded animal that internally regulates its body temperature to keep it at a constant level.

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Cephalization

The concentration of sensory organs and nerve cells at the anterior (front) end of an animal.

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Key Characteristics of Animals

• Animals are multicellular eukaryotes, with bodies made of many complex cells.

• ​They are heterotrophs, meaning they must eat other organisms for nutrients.

• Their cells lack cell walls, which allows for greater mobility and flexibility.

• Most animals reproduce sexually and have adaptations for finding and digesting food.

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Multiple Choice

Which of the following is a defining characteristic of the Animal Kingdom?

• They have cell walls and are autotrophs.

• They are unicellular and make their own food.

• They are multicellular, heterotrophic, and have no cell walls.

• They are eukaryotes that reproduce asexually.

Body Plans and Symmetry

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Bilateral Symmetry

• A single line divides the animal into two mirror-image halves.

• This plan creates a distinct left side and a right side.

• Sensory organs are often gathered at the animal's front end.

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Radial Symmetry

• Body parts are arranged in a circle around a central point.

• Many lines can divide the animal into equal, pie-like sections.

• This is common in animals like jellyfish and sea anemones.

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Asymmetry

• These animals do not have a definite or particular body shape.

• Sponges are a classic example of this very simple body plan.

• Their body structure shows no symmetry in any possible way.

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Solved Example 1
A newly discovered invertebrate has a soft, segmented body and a protective outer shell. It is observed to have bilateral symmetry. Classify this animal into its most likely phylum and provide a brief justification for your choice.

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Step 1: Analyze and Sketch the Problem

• Goal: Classify the unknown invertebrate into its phylum.

• Knowns: Soft, segmented body; protective outer shell; bilateral symmetry.

• Unknown: The animal's phylum.

• Relevant Phyla: Porifera (sponges), Cnidaria, Platyhelminthes (flatworms), Nematoda (roundworms), Annelida (segmented worms), Mollusca (mollusks), Arthropoda, Echinodermata.

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Solved Example 1
A newly discovered invertebrate has a soft, segmented body and a protective outer shell. It is observed to have bilateral symmetry. Classify this animal into its most likely phylum and provide a brief justification for your choice.

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Step 2: Solve for the Unknown

• Eliminate Porifera (asymmetrical) and Cnidaria/Echinodermata (radial symmetry) because the animal has bilateral symmetry.

• The animal has a soft body and a shell, which are key characteristics of the Phylum Mollusca.

• While some worms (Annelida) are segmented, the presence of a distinct shell strongly points towards Mollusca. Arthropods have exoskeletons, not typically called shells in this context.

• Therefore, the animal most likely belongs to the Phylum Mollusca.

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Solved Example 1
A newly discovered invertebrate has a soft, segmented body and a protective outer shell. It is observed to have bilateral symmetry. Classify this animal into its most likely phylum and provide a brief justification for your choice.

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Step 3: Evaluate the Answer

• Justification: The combination of a soft body, a protective shell, and bilateral symmetry are defining features of the Phylum Mollusca. This fits the description better than any other phylum.

• Example: Common mollusks like snails (Gastropods) and clams (Bivalves) fit this description perfectly.

Multiple Choice

An animal has a body plan where its sensory organs are concentrated at its front end, and a single line can divide it into two mirror images. How would you describe its symmetry and structure?

• Radial symmetry with cephalization

• Radial symmetry with no cephalization

• Asymmetric with no cephalization

• Bilateral symmetry with cephalization

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Invertebrates: The Majority

Sponges (Phylum Porifera)

• Sponges are very simple animals that do not have any tissues or organs.

• Their bodies are asymmetrical, meaning they do not have a balanced shape or form.

• They feed by filtering water through tiny openings, called pores, to get their food.

Cnidarians

• This group includes animals such as jellyfish, sea anemones, and corals.

• They have bodies with radial symmetry, arranged around a central point like a wheel.

• They use special stinging cells on their tentacles to capture prey for food.

Multiple Choice

What are the key differences between Sponges and Cnidarians mentioned in the slide?

• Sponges have bilateral symmetry and stinging cells; Cnidarians are asymmetric and use pores.

• Sponges are asymmetric and strain food through pores; Cnidarians have radial symmetry and use stinging cells.

• Sponges have radial symmetry and pores; Cnidarians are asymmetric and have stinging cells.

• Both are asymmetric, but only Cnidarians have stinging cells.

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Invertebrates: Worms and Mollusks

Worms

• The three main phyla of worms all have bilateral symmetry, meaning two identical halves.

• Flatworms are thin and often parasitic, while roundworms possess long and circular bodies.

• Segmented worms, like earthworms, have bodies that are divided into many ringed sections.

Mollusks

• Mollusks are soft-bodied animals, and most are protected by a hard outer shell.

• The main groups are gastropods (snails, slugs) and bivalves (clams, oysters).

• Cephalopods are another main group that includes intelligent animals like squid and octopuses.

Multiple Choice

Which characteristic is used to distinguish segmented worms from flatworms and roundworms?

• Their parasitic nature

• A body divided into many ringed sections

• The presence of a protective shell

• The presence of a soft body

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Invertebrates: Arthropods and Echinoderms

Arthropods

• ​This is the largest group of invertebrates, characterized by segmented bodies and jointed legs.

• ​​They have a hard external skeleton, known as an exoskeleton, which is made of chitin.

• ​To grow, they shed their exoskeleton through a process called molting. Arachnids are arthropods without antennae.

Echinoderms

• ​These marine animals, including sea stars and sea urchins, have radial symmetry as adults.

• ​​A key feature of this group is the presence of skin covered with spines.

• ​They move around by using thousands of tiny, tube-like feet on their undersides.

Multiple Choice

What is a major feature of Arthropods that requires them to molt?

• Their radial symmetry

• Their spiny skin

• Their hard exoskeleton made of chitin

• Their use of tube-like feet for movement

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Vertebrate Body Temperature Regulation

Ectotherms

• Ectotherms are animals that are commonly called “cold-blooded.”

• Their body temperature changes depending on their external surroundings.

• They rely on external sources like sunlight to regulate body heat.

Endotherms

• Endotherms are animals that are commonly known as “warm-blooded.”

• They internally regulate their body temperature to keep it constant.

• This allows them to survive in a wide range of different climates.

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Solved Example 2
A 25 kg ectothermic reptile's body temperature is 22°C. The ambient temperature drops, causing the reptile's temperature to decrease by 15%. What is the reptile's new body temperature in degrees Celsius?

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Step 1: Analyze and Sketch the Problem

• Goal: Determine the new body temperature of the reptile.

• Knowns: Initial temperature = 22°C, Percentage decrease = 15%. The reptile's mass of 25 kg is extra information not needed for this calculation.

• Unknown: Final temperature.

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Solved Example 2
A 25 kg ectothermic reptile's body temperature is 22°C. The ambient temperature drops, causing the reptile's temperature to decrease by 15%. What is the reptile's new body temperature in degrees Celsius?

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Step 2: Solve for the Unknown

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Solved Example 2
A 25 kg ectothermic reptile's body temperature is 22°C. The ambient temperature drops, causing the reptile's temperature to decrease by 15%. What is the reptile's new body temperature in degrees Celsius?

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Step 3: Evaluate the Answer

• The reptile is an ectotherm, so its body temperature changes with the surroundings. A drop in ambient temperature causing a decrease in body temperature is consistent with this.

• The final temperature of 18.7°C is a 15% decrease from 22°C, so the calculation is correct.

Multiple Choice

What is the key difference between an ectotherm and an endotherm?

• Ectotherms have a backbone, while endotherms do not.

• Ectotherms have a body temperature that changes with their surroundings, while endotherms keep it constant.

• Ectotherms regulate their temperature internally, while endotherms rely on their surroundings.

• Ectotherms have an endoskeleton, while endotherms have an exoskeleton.

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Vertebrates: Fish and Amphibians

Fish

• Fish are ectotherms that live in water and breathe using gills to get oxygen.

• They possess a unique organ called a swim bladder to control their buoyancy.

• Their group includes bony fish, cartilage fish like sharks, and primitive jawless fish.

Amphibians

• Amphibians are ectotherms that lead a "double life" in water and on land.

• They undergo a body change from larva to adult which is called metamorphosis.

• They have thin, moist skin for breathing and must lay their eggs in water.

Multiple Choice

Why is an amphibian's life described as a 'double life'?

• Because they spend part of their life in water and part on land.

• Because they have both gills and lungs at the same time.

• Because some have bones and others have cartilage.

• Because they can be both ectothermic and endothermic.

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Vertebrates: Reptiles and Birds

Reptiles

• Reptiles are ectotherms, meaning they depend on external sources for body heat.

• Their bodies are covered in scaly, watertight skin which helps prevent water loss.

• They breathe with lungs and most species lay soft-shelled eggs on the land.

Birds

• Birds are endotherms, meaning they can generate their own internal body heat.

• They have feathers for flight and insulation, and have lightweight, hollow bones.

• Birds breathe with lungs and reproduce by laying hard-shelled eggs, often in nests.

Multiple Choice

Which adaptation allows reptiles to live on land more effectively than amphibians?

• Having scaly, watertight skin

• Being endothermic

• Having hollow bones

• Undergoing metamorphosis

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What are Mammals?

• Mammals are warm-blooded vertebrates that are covered in hair or fur.

• ​They have mammary glands to produce milk and feed their young.

• Most have complex brains and give birth to live young.

• Some mammals, like the duck-billed platypus, lay eggs instead.

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Solved Example 3
A newly discovered mammal maintains a stable body temperature of 37°C, even when the outside temperature drops to 10°C. If 97% of all animal species are invertebrates, how many mammal species are there?

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Step 1: Analyze and Sketch the Problem

• Goal: Determine the number of mammal species.

• Knowns: The mammal is an endotherm, maintaining a constant body temperature. 97% of animal species are invertebrates.

• Unknown: The total number of mammal species.

• Limitation: The provided text gives a percentage for invertebrates but does not provide the total number of animal species, nor does it give a formula to calculate the number of mammal species.

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Solved Example 3
A newly discovered mammal maintains a stable body temperature of 37°C, even when the outside temperature drops to 10°C. If 97% of all animal species are invertebrates, how many mammal species are there?

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Step 2: Solve for the Unknown

• The problem cannot be solved with the given information. The percentage of invertebrates (97%) is provided, which means vertebrates make up 3% of animal species.

• However, mammals are just one class of vertebrates. We do not have information on what percentage of vertebrates are mammals.

• There is no mathematical formula or calculation method taught in the source material to solve this kind of problem.

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Solved Example 3
A newly discovered mammal maintains a stable body temperature of 37°C, even when the outside temperature drops to 10°C. If 97% of all animal species are invertebrates, how many mammal species are there?

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Step 3: Evaluate the Answer

• It is not possible to perform a calculation or evaluate an answer. The question is designed to test conceptual understanding rather than mathematical skill.

• The key takeaway is that mammals are a small fraction of the total animal kingdom, which is dominated by invertebrates. No numerical solution is expected based on the lesson content.

Multiple Choice

What two characteristics are unique to mammals compared to other vertebrate classes mentioned?

• Having a complex brain and giving birth to live young

• Being warm-blooded and having a backbone

• Having hair or fur and producing milk from mammary glands

• Being endothermic and laying eggs

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Common Misconceptions About the Animal Kingdom

Misconception	Correction
All long, thin-bodied animals are the same type of worm.	Worms belong to three distinct phyla: flatworms, roundworms, and segmented worms.
Spiders are insects.	Spiders are arachnids, not insects, because they lack antennae.
All vertebrates are warm-blooded.	Only birds and mammals are warm-blooded; others are cold-blooded.
All animals give birth to live young.	Most animal species, including some mammals like the platypus, lay eggs.

Multiple Choice

An organism is a multicellular heterotroph with no cell walls and reproduces sexually. Based on these characteristics, in which kingdom would you classify it and why?

• Animalia, because it is a multicellular heterotroph with no cell walls.

• Fungi, because it is a heterotroph.

• Plantae, because it is multicellular.

• Protista, because it reproduces sexually.

Multiple Choice

What is a key functional difference between an endoskeleton, found in vertebrates, and an exoskeleton, found in arthropods?

• An endoskeleton is for protection only, while an exoskeleton is for movement.

• An endoskeleton grows with the animal, while an exoskeleton is non-living and must be shed.

• There is no functional difference between them.

• An endoskeleton prevents movement, while an exoskeleton allows for it.

Multiple Choice

A scientist discovers a new deep-sea animal that is asymmetric, has no tissues, and appears to filter food from the water. Predict which invertebrate phylum this animal most likely belongs to and justify your reasoning.

• Cnidaria, because it lives in the sea.

• Mollusca, because it has a soft body.

• Porifera (Sponges), because it is asymmetric and filter-feeds through pores.

• Arthropoda, because it is an animal.

Multiple Choice

Analyze the adaptations for terrestrial life by comparing amphibians and reptiles. Why are reptiles generally less dependent on water for reproduction?

• Reptiles are endothermic, which allows them to live in dry areas.

• Amphibians undergo metamorphosis, which makes them dependent on water.

• Amphibians have lungs, while reptiles have gills.

• Reptiles have scaly, watertight skin and lay shelled eggs on land, unlike amphibians who need water.

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Summary

• Animals are multicellular heterotrophs with body plans showing specific symmetries.

• The Animal Kingdom is divided into invertebrates and vertebrates.

• Major invertebrate phyla exist, while vertebrates include fish, amphibians, reptiles, birds, and mammals.

• Vertebrates can be ectothermic or endothermic, with adaptations for diverse environments.

Poll

On a scale of 1-4, how confident are you about classifying animals into their major groups?

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• 3

• 4