Specialised cells

To solve this, remember secondary growth in woody plants. Secondary growth is what increases the stem or root’s thickness (its girth). It happens because lateral meristems keep dividing and producing new tissues that build up into wood and bark.

Now consider the tissues linked to the outside of the stem. The cork cambium makes the periderm (outer bark). Even though it’s important for protection, it doesn’t create the inner, solid material we call wood.

The vascular cambium is a narrow ring of dividing (meristem) cells. It produces new xylem and phloem, so it’s the producer of wood, but because it’s only a very thin layer, it isn’t the main substance of wood.

The secondary phloem is made by the vascular cambium on the outer side and carries sugars through the plant. In woody stems, this tissue contributes to the inner bark and is often compressed or shed over time, so it doesn’t build up as the bulk of wood.

From plant anatomy, wood is secondary xylem.

The vascular cambium adds secondary xylem toward the inside of the stem. These cells develop thick, lignified walls (with lignin for strength). Because new layers are added year after year, they accumulate to form most of the trunk’s solid, supportive material.

We need the tissue that makes up the wood. In biology, wood means the built-up, supportive material formed during secondary growth. We can eliminate options until only the correct tissue remains.

Eliminate Vascular cambium (Option C) and Cork cambium (Option D).

Both are meristematic tissues, meaning they are thin layers of actively dividing cells. They create new tissues during secondary growth, but they are not the thick, structural material that we recognize as wood—more like the production line than the final material.

Next eliminate Secondary phloem (Option B).

In secondary growth, phloem is produced to the outside of the vascular cambium and contributes to the bark. As the stem expands, this phloem is often crushed or lost, so it doesn’t accumulate into the hard inner mass of wood.

That leaves Secondary xylem.

In woody plants, secondary xylem is produced inward by the vascular cambium. Its cells have thick walls strengthened by lignin, which provides strong support. Over many years, these xylem layers pile up to form wood, helping both with support and with water transport.

First, remember the order of organization in organisms made of many cells:

1. Cell: the smallest living unit (for example, one muscle cell).
2. Tissue: many similar cells working as a group (for example, muscle tissue).
3. Organ: a body structure built from multiple tissue types that cooperate to do a particular function.
4. Organ System: several organs working together (for example, the digestive system).

Now consider the heart and the stomach.

• The heart includes cardiac muscle, connective tissue, and nervous tissue that coordinate so it can move blood around the body.
• The stomach contains muscle tissue for mixing, epithelial tissue for lining and protection, and glandular tissue that releases digestive chemicals.

Because each structure combines several tissues to carry out a complex task, each one matches the definition of an organ.

A cell is one tiny unit of life. Even though the heart and stomach are built from enormous numbers of cells, each structure is far more complex than a single cell, so this level doesn’t fit.

A tissue is mainly one type of cell (or very similar cells) working together. The heart and stomach each contain multiple different tissues (such as muscle and nerve), so they are more than just a tissue.

An organ system is made of several organs working together. The heart belongs to the circulatory system, and the stomach belongs to the digestive system. Each of these is only one part of a larger system, not the whole system.

Since the heart and stomach are each built from different tissues that work together for a specific role, they are best classified as organs.

To sort the heart or stomach into the correct category, use the standard organization ladder in biology:

$\text{Cell}\to \text{Tissue}\to \text{Organ}\to \text{Organ System}\to \text{Organism}$

A cell is the basic building block (like one muscle cell). The heart and stomach are made from huge numbers of specialized cells arranged into working parts, so they are much higher than the cell level.

A tissue is a collection of similar cells doing a shared function (such as cardiac muscle tissue). But the heart includes several tissues—muscle, connective, and nervous tissue—working together, so it cannot be classified as just one tissue.

An organ system is multiple organs cooperating for a major body process. The heart is one organ within the circulatory system, and the stomach is one organ within the digestive system. Therefore, neither one alone is an organ system.

An organ is made of different tissues working together to perform a particular function. That describes the heart (moving blood) and the stomach (breaking down food), so organ is the correct level.

To answer this, start by remembering what biologists mean by a tissue. In levels of organisation, a tissue is a collection of cells that are alike and cooperate to achieve one shared job.

This idea is central in the MYP Organisms topic. If you understand how cells group into tissues, it becomes much easier to understand how organs and organ systems function as larger units.

Consider the first option: it implies a tissue is built from lots of different kinds of cells. But a tissue is made from similar cells. When you have several different tissues working together, that forms an organ (for example, a heart or a leaf), not one tissue.

The next statement suggests cells don’t need to coordinate. If cells in a tissue behaved independently, the tissue couldn’t carry out complex actions—like muscle fibres contracting together or gland cells releasing hormones at the right time. Tissues depend on teamwork and coordination, not isolated cell behaviour.

This option says cells give up their specialised roles when they join a tissue. In reality, the reverse happens. Cells go through differentiation and become more specialised, so they can do their particular job in that tissue more effectively.

Using the definition and eliminating the inaccurate choices, Option D fits best. It recognises that a tissue contains many cells of the same (or very similar) type and that they coordinate what they do. Together they can produce an outcome a single cell could not achieve alone (an emergent property).

To solve this, first recall the definition of a tissue from the Organisms topic. A tissue is a group of similar cells that cooperate to carry out a particular function.

An important linked idea is emergent properties: as cells work together, the tissue can do things that one cell alone cannot.

Option A suggests that different types of cells come together to make a tissue.

However, when different tissues combine and work as one unit, that structure is an organ (such as the heart or a leaf). A tissue is made of the same or very similar cells, so this option doesn’t match biology.

Option B says the cells function independently.

If tissue cells acted separately, they wouldn’t be able to produce coordinated actions like a muscle contracting as one or nerve signals being passed along properly. The defining feature of a tissue is cooperation, not independence, and independent behaviour would not create the efficiency seen in complex organisms.

Option C asks us to believe that cells become less specialised when forming a tissue.

Actually, cells become specialised through differentiation to carry out specific roles. For instance, muscle cells become adapted for contraction. They don’t lose specialisation; they rely on it to help the tissue function.

Once the incorrect choices are removed, the best description is clear.

A tissue contains many cells of the same type (or very similar types) that coordinate their behaviour. This teamwork allows the tissue to perform a complex function that a single cell cannot achieve on its own, which is exactly how multicellular organisms operate.

In biology, emergent properties mean that “the whole can do more than the individual parts.”

So, while one cell can complete basic life processes, it cannot carry out the full function of a tissue (like pumping blood or sending a coordinated signal) by itself. This is a key idea in Topic: Organisms in your course.

Next, recall the definition of a tissue. In the IB curriculum, a tissue is described as a group of similar cells (the same cell type) that have specialised in similar ways to perform a particular function.

With this in mind, you can judge each option more accurately.

Apply elimination using what you know:

• Option A is wrong because tissues consist of similar cells; combining different tissues gives an organ, not one tissue.
• Option B is wrong because emergent properties require cells to interact; independent cells wouldn’t create a shared tissue-level function.
• Option C is wrong because cells generally gain specialisation through differentiation when forming tissues; they don’t discard it.

The best description is that many cells of the same type act together in a coordinated way, producing a result no single cell could manage.

For example, one heart muscle cell can contract, but only millions contracting in a coordinated pattern can pump blood effectively—an excellent example of an emergent property.

We are looking for one plant tissue that does both of these things at once: (1) moves water through the plant and (2) helps the plant stay rigid/upright. In MYP Biology, that combination points to a vascular tissue with strong supporting features built into it.

Mesophyll is found inside leaves (palisade and spongy layers). Its key role is capturing light for photosynthesis and allowing gases to move around in the leaf. It isn’t designed for moving large amounts of water through the whole plant or for acting as a main support tissue.

Phloem is part of the transport system, but it mainly carries dissolved food substances (such as sucrose and amino acids) from where they’re made to where they’re needed. Because phloem cells are living and not heavily strengthened like woody tissues, it isn’t the main tissue responsible for providing the plant’s structural framework.

The epidermis forms the plant’s outer covering. It protects the plant and, with its waxy cuticle, helps reduce water loss. However, it doesn’t function as the internal pipeline for water movement through the plant, and it isn’t the primary tissue that supports the plant from the inside.

Xylem is the tissue adapted for both tasks:

• Water Transport: It is made of long, hollow tubes (vessels and tracheids) that are dead at maturity, creating an open pathway for water to travel from roots up to the leaves.
• Structural Support: Xylem walls are reinforced with lignin, making them thick and tough, which helps the plant stay upright and resist bending.

To answer this, we need a tissue that can do two things: move water through the plant and add structural support. We’ll rule out any option that doesn’t meet both of these requirements.

Mesophyll is a leaf tissue full of chloroplasts, mainly for photosynthesis. It isn’t the plant’s long-distance water transport system and it doesn’t provide the main mechanical strength for the whole plant, so it can’t be the best answer.

Phloem does transport materials, but it transports sugars and other organic solutes (translocation), not water. Also, because sieve tube elements must stay alive, they don’t have the heavy lignin strengthening seen in major support tissues.

The epidermis is the plant’s protective outer layer. Its job is to act as a barrier and help prevent dehydration, not to move water internally from roots to leaves.

The remaining option is Xylem, and it matches both requirements:

• It forms hollow, dead tubes (vessels and tracheids) that efficiently carry water and minerals upward.
• Its walls contain lignin, which makes the tissue strong and provides the structural support needed for upright growth.

So xylem is the correct choice.

To solve this, start with the meaning of analogous structures. These are features found in different organisms that:

1. Do the same (or very similar) job.
2. Did not come from the same ancestral structure for that trait (they arose separately).

This idea links to Topic 5: Evolution (unity and diversity) and is often explained by convergent evolution, where unrelated groups end up with similar solutions to similar problems.

A key part of being analogous is that the similarity is not because the trait was inherited from a shared ancestor. Plants and animals are in different kingdoms and split extremely long ago, so their “surface-covering tissues” were not inherited from one original covering tissue.

So, any choice suggesting a shared starting point should be removed.

Now consider the cell biology. Plant epidermal cells are plant cells, so they typically have a cellulose cell wall and a large central vacuole. Animal epithelial cells are animal cells and do not have cellulose cell walls.

That means this statement cannot correctly describe both tissues, so it cannot be the reason they’re called analogous.

Analogous comparisons are mainly based on function. Plant epidermal tissue (covering leaves, stems, and roots) and animal epithelial tissue (such as skin and internal linings) both act as an outer barrier. Their main role is to cover surfaces and protect the organism from the environment.

Because these tissues do a similar protective, surface-covering job but come from very different evolutionary backgrounds and are built differently, the best explanation is the one describing their shared function.

Using elimination, begin by separating analogous from homologous.

• Analogous structures: Similar function, but different evolutionary origin (for example, insect wings vs bird wings).
• Homologous structures: Similar origin or developmental pathway, even if the function changes (for example, forelimbs in humans and whales).

Since the question already says the tissues are analogous, we should look for a match in function, not shared origin or development.

Any option claiming a common evolutionary source or the same embryonic germ layer would point to homology, not analogy. Also, plants and animals evolved multicellularity and tissues separately, and plants don’t have animal-style embryonic germ layers like ectoderm and endoderm.

So these origin-based options should be crossed out.

Check the option about cell structure. Plant cells do have cellulose walls and large vacuoles, but animal epithelial cells do not have a cellulose wall at all. Since the statement doesn’t apply to animal tissue, it cannot explain the classification.

The remaining idea is the functional one. Both tissues form a surface layer that covers the organism and helps protect it. That shared role is exactly what makes them analogous.

We need to match an animal tissue to the roles listed: giving the body support, holding parts together, and storing substances such as fat. These functions are part of what you learn in the Organisms: Tissues topic area of the course.

Muscular tissue is mainly designed to shorten (contract) so it can create movement. Even though it is vital, it is not best known for sticking structures together or acting as a fat storage tissue.

Epithelial tissue forms sheets that cover body surfaces and line organs and cavities (for example, skin or the gut lining). Its typical functions include protection, absorption, and secretion, not providing a supportive framework or storing fat.

Nervous tissue is used for fast communication and coordination. It senses changes and sends electrical messages (impulses), rather than acting like the body’s structural support or “binding material.”

By definition, Connective tissue includes several types that do exactly what the question describes: bone and cartilage provide support, tendons and ligaments connect and bind structures, and adipose tissue stores fat. This matches every function listed.

To answer by elimination, focus on the roles given: a tissue that provides support, helps join/bind body parts, or stores fat.

This is covered in the Organisms unit under Tissues in the IB Biology syllabus.

Muscular tissue’s main feature is contraction, which produces movement (like moving your limbs, pumping blood, or pushing food through the digestive system). Since its primary purpose is not binding structures or storing fat, it is not the best match.

Epithelial tissue is the body’s covering and lining tissue (such as skin and organ linings). It is strongly linked to protection, absorption, and secretion, not to forming supportive structures or storing fat.

Nervous tissue specializes in sending information around the body by transmitting electrical signals. It does not act as a connector between structures or as a fat storage tissue.

After eliminating the others, Connective tissue remains. This group is varied and fits the description well:

• Support & Binding: Bone, cartilage, tendons.
• Storage: Adipose tissue (fat) stores energy and helps with insulation.

So, this is the correct choice.

To solve this, start by recalling the job of mesophyll tissue. In MYP Biology (Metabolism: Photosynthesis), the palisade and spongy mesophyll layers are taught as the key leaf tissues where most photosynthesis happens.

Photosynthesis can only happen if cells can take in light energy. Mesophyll cells are adapted for this by having many chloroplasts, which contain chlorophyll. A high number of chloroplasts helps the tissue absorb more light and carry out its role efficiently.

Structures in living things are usually positioned where they can do their job well.

• Leaves are shaped and positioned to collect sunlight.
• Roots are usually underground, so they receive little to no light.

Because mesophyll depends on light to drive photosynthesis, it makes sense that it is found in leaves rather than roots.

Now remove the distractors:

• Option A: Moving water is mainly handled by xylem tissue, not mesophyll, so this doesn’t explain mesophyll’s location.
• Option B: Plants have an epidermis; “epithelial tissue” is an animal term, so this option mixes up kingdoms.
• Option C: Mesophyll (especially spongy mesophyll) helps gas exchange, but it is not its only purpose, and gas exchange alone wouldn’t limit it to leaves because roots also exchange gases with the soil air spaces.

The best explanation is that mesophyll is concentrated in leaves because it is specialized for absorbing light for photosynthesis, which requires many chloroplasts. That matches the final option.

Begin by remembering what mesophyll tissue refers to. In Biology MYP topics on Tissues and Photosynthesis, mesophyll is the internal tissue of a leaf that is adapted to carry out photosynthesis, and that process needs sunlight. Leaves are exposed to light, while roots are generally in darkness underground, so the tissue’s location is an adaptation.

Option A suggests roots don’t need water transport. That’s wrong because roots are the main place where water enters the plant. Also, the tissue specialized for transporting water is xylem, not mesophyll. So the statement is incorrect in more than one way.

Option B talks about “animal-like epithelial tissue.” Plants and animals have different tissue types: plants have epidermal tissue, while animals have epithelial tissue. Since roots do not have animal tissue, this option is not biologically valid.

Option C claims mesophyll is for gas exchange “only.” Although spongy mesophyll has air spaces that support gas movement, the word “only” makes the claim too narrow. Mesophyll’s central role is photosynthesis, and gas exchange by itself wouldn’t require the tissue to be mainly in light-exposed leaves.

After eliminating A, B, and C, Option D remains. This fits what we know: mesophyll (especially palisade mesophyll) contains many chloroplasts. Chloroplasts absorb light energy for photosynthesis, so this tissue is found in leaves where light is available, not in roots where light is absent.

Living things are described using levels that go from simple to complex. To answer, we need the level that comes after a cell but before an organ. In the Organisms topic, that level is called tissues.

In biology, a tissue is made of cells that are alike (often from the same origin) and that cooperate to carry out one specific function.

For cells to count as a tissue, they must meet two key conditions:

1. They are similar in their structure and where they come from.
2. They are specialized so they can perform the same shared task effectively.

Use the levels of organization to remove wrong choices:

• Option A is describing an organ system (for example, digestive or respiratory), which is above organs and therefore above tissues.
• Option B refers to just one cell (like a unicellular organism), not a group of cells.
• Option C doesn’t fit because tissues are arranged in an organized way; they are not simply a scattered or random set of cells in the body.

Option D fits the definition exactly: it says the cells are similar, have special roles, and work together to achieve one particular function.

To identify the correct meaning of tissue, eliminate choices that match other levels in the biological hierarchy:

$\text{Cells}\to \text{Tissues}\to \text{Organs}\to \text{Systems}\to \text{Organisms}$

This comes from the Organisms topic, where you learn how these levels connect.

Option A talks about multiple organs working together to complete a big body function. That is an organ system (such as the digestive system), which is not the same as a tissue and is much higher in organization.

Option B describes a single cell that can carry out life processes. Even if that can be true for unicellular organisms, a tissue must involve many cells working together, so this cannot be correct.

Option C suggests cells are just grouped randomly. In real tissues, cells are arranged and coordinated; they usually share similar features and a common origin so they can function as a unit. A random mixture of cells is not a tissue.

After eliminating A, B, and C, Option D remains. It matches the biological definition: a tissue is a set of similar cells (such as nerve cells or muscle cells) adapted to carry out one shared function.

We need to name the level of organization based on what it is built from. The clue is that it includes multiple tissue types cooperating to carry out one particular job.

Multicellular living things are arranged in levels from simple to complex. In the Organisms part of the syllabus, the usual order is:

1. Cells: The smallest living units.
2. Tissues: Collections of similar cells doing the same general role.
3. Organs: Structures made from different tissues working together.
4. Organ Systems: Groups of organs that cooperate.
5. Organism: The entire living individual.

Now compare each option to the phrase “different tissues working together”:

• Specialised cell: only one cell, so it cannot be made of several tissues.
• Colony: usually means many separate organisms (or similar cells) living close together, not an internal working unit within one organism.
• Organ system: this is a broader level made of multiple organs, which is beyond what is described.

In the hierarchy, an organ (for example, a heart or a leaf) is defined as a structure containing several different tissues that work together to achieve a shared function.

This can be solved by applying the standard levels of organization in multicellular organisms:

$\text{Cells}\to \text{Tissues}\to \text{Organs}\to \text{Organ Systems}\to \text{Organisms}$

The key detail is that more than one tissue type is involved in doing one job.

A specialized cell is a single cell. Since tissues are built from many cells, and the question is about multiple tissues working together, a cell is too simple to fit.

A colony describes many organisms (or similar cells) living in the same area, such as a bacterial colony. It is not one of the usual internal organization levels inside one multicellular organism.

An organ system is made from multiple organs that work together (for example, the digestive system). That is one level above the “different tissues working together” description.

An organ sits directly above tissues in the hierarchy. It is formed from several tissue types (such as muscle, epithelial, connective, and nervous tissues) that coordinate to carry out a specific function, which matches the definition exactly.

A good way to explain tissue differences is to start with lifestyle. Most animals are motile (able to move), so they depend on tissues that support movement and fast communication, such as muscle tissue and nervous tissue.

Plants are sessile (they remain rooted). Since they can’t walk away from danger or search for food, their tissues are adapted for holding the plant upright and for moving water and dissolved sugars around the body over long distances (for example, xylem and phloem). These different survival strategies shape how their tissues are organized.

Plants and animals are both multicellular organisms with many cell types. Each relies on specialized cells that carry out particular roles. For instance, plants have guard cells that regulate gas exchange, and animals have red blood cells that carry oxygen. So it’s wrong to claim specialization exists only in animals.

This choice mixes up the main functions. Animals typically have well-developed muscle and nerve tissues to enable movement and quick responses. Although plants can show limited movements (like bending toward light or a Venus flytrap snapping shut), their tissue organization is mainly about photosynthesis, support, and transport—not traveling from place to place.

Living things are often described using a hierarchy: $\text{Cells}\to \text{Tissues}\to \text{Organs}\to \text{Systems}$

Plants match this pattern too. Plant tissues (such as epidermal tissue) make up organs (like leaves), and these organs belong to larger systems (like the shoot system). So plants definitely do have hierarchical organization.

The best explanation is that plants are fixed in place and must make their own food through photosynthesis. That leads to tissues adapted for strong support (so they can grow upright without an internal skeleton) and for efficient transport of water, minerals, and sugars. Animals, in contrast, emphasize tissues that support movement and rapid coordination.

We’re comparing how plants and animals arrange cells into tissues. Using the Process of Elimination, we can test each option against what we know about tissues, organs, and systems from the Organisms topic.

Option A says only animals have specialized cells. But plants clearly have specialized cells too—such as root hair cells for absorbing water and minerals, and guard cells for controlling gas exchange. So this option doesn’t match biological evidence.

Option D conflicts with the standard hierarchy: $\text{Cells}\to \text{Tissues}\to \text{Organs}\to \text{Systems}\to \text{Organism}$ Plants have organs (like roots and leaves) and systems (like the vascular system and the shoot/root systems). Since plants do follow this organization, the statement is false.

Option C suggests plants are designed for movement and animals are not, which is the opposite of what we observe. Animals rely on muscle and nerve tissues for locomotion. Plants may respond by growing toward stimuli (tropisms), but they do not relocate their whole bodies. Therefore, this option is incorrect.

With the incorrect choices removed, Option B remains. It matches core biology: because plants are stationary, their tissues are strongly shaped by needs like support and long-distance transport, while animals prioritize tissues for movement and fast responses.

To answer this, focus on the comparison built into the sentence. It sets up two situations:

1. One muscle cell working by itself.
2. Millions of muscle cells working at once.

The word "but" signals that the second situation should contrast with the first.

The connector "but" tells us the second part should describe something different from (and stronger than) the first part.

First part: $\text{One cell}\to \text{contracts weakly}$

Second part mentions "millions," which implies the combined effect should be much larger.

Now rule out answers that don’t match the expected contrast or the role of muscle cells:

• Option A doesn’t work because "weak movement" doesn’t oppose the idea of a weak single-cell contraction.
• Option B doesn’t fit because muscles respond to nerve signals; they aren’t described as producing signals as the movement output.
• Option C doesn’t fit because sugar (glucose) is used up to supply energy; it isn’t what the contraction produces as a result.

If one muscle cell only gives a weak contraction, then many muscle cells contracting together will add their forces, creating a much stronger effect. That larger force is what allows noticeable body movement.

So the blank should be filled with "strong movement."

The prompt contrasts what happens when one muscle cell contracts versus when "millions" contract together. The blank asks for what these cells produce together that can "move a body part."

This links to Topic: Organisms (Tissues and Systems) in MYP Biology, where many specialised cells working together create a bigger function than one cell alone.

Because the sentence begins with a weak contraction from one cell, it would not make sense for millions of cells together to still cause only "weak movement." The word "but" tells you the result should be the opposite of weak.

Muscle tissue needs sugar (glucose) as fuel and receives signals from the nervous system, but neither of these is the movement produced.

• Sugar provides energy; it isn’t the force or motion.
• Signals are instructions; they aren’t the physical result.

After eliminating the other choices, the only option left describes the correct physical outcome. When many small contractions happen together, their forces add up to create strong force and noticeable movement.

To decide, think about how body structures are arranged. Biology describes a sequence of organization:

$\text{Cells}\to \text{Tissues}\to \text{Organs}\to \text{Systems}\to \text{Organism}$

This question is focused on the organ stage in that sequence. You can connect this idea to the Organisms section of your course.

An organ is understood as a body structure made from several tissue types that cooperate to carry out a bigger job than any single tissue could do alone. Although an organ needs at least two tissue types, most animal organs commonly include all four major tissue types working together:

1. Epithelial tissue: forms coverings and linings (for example, the stomach’s inner lining).
2. Connective tissue: holds, supports, and links parts (such as supportive layers and structures within an organ).
3. Muscle tissue: produces movement or force (like squeezing, pumping, or mixing).
4. Nervous tissue: carries messages that help control and coordinate what the organ does.

The statement says the tissues appear in “different proportions,” which makes sense because an organ’s main function determines which tissue is most abundant.

For instance, the heart contains mostly muscle for strong contractions, but it also includes epithelial tissue for smooth linings, connective tissue for support and valves, and nervous tissue for timing and coordination signals.

Because complex organs are typically built from multiple tissues integrated into one working structure, we can compare the choices and decide which one matches this biological idea.

This is a core idea in animal structure: most complex organs rely on the combined roles of epithelial, connective, muscle, and nervous tissues to function properly, even if one type is much more common than the others.

Before judging the statement, bring to mind the four major tissue types from Topic: Tissues:

1. Epithelial tissue: covers body surfaces and lines internal spaces.
2. Muscle tissue: contracts to create movement.
3. Connective tissue: supports, binds, and protects (including tissues like bone and blood).
4. Nervous tissue: sends electrical signals for control and communication.

Using Specific Example Analysis, choose a well-known complex organ such as the heart and check whether each tissue type shows up:

• Muscle tissue: most of the heart is cardiac muscle (myocardium) that generates the pumping action.
• Epithelial tissue: the heart has smooth protective linings—endocardium on the inside and pericardium around the outside.

Continuing with the heart:

• Connective tissue: tough fibrous tissue helps form valves and provides strength and shape; also, blood moving through the heart counts as a fluid connective tissue.
• Nervous tissue: specialized conducting tissue (such as the SA node) produces electrical signals that set the rhythm for contractions.

So even though the proportions are not equal (there is far more muscle than nervous tissue), all four tissue types are present.

Since the heart clearly depends on all four tissue types to do its job, it supports the idea that many animal organs are built the same way. Organs like the lungs or stomach also combine multiple tissues, just in different mixes depending on their roles.

Because the heart example demonstrates that the four tissue types can all be found within one organ, the option claiming the statement is incorrect should be ruled out.

The statement matches how most complex animal organs are organized, so the correct choice is True.