All of the following statements are correct for blue green algae, except

Options

A. they have chlorophyll- a, which is also found in higher plants.
B. they may be filamentous, colonial , or unicellular.
C. they have heterocysts which are clear cells without chlorophyll.
D. they are connecting link between plants and animals.

Answer

To solve the question regarding blue-green algae, we need to evaluate each of the given statements and identify the one that is incorrect. Here’s a step-by-step breakdown of the solution:

### Step 1: Analyze the First Statement
**Statement:** Blue-green algae have chlorophyll A, which is also found in higher plants.
- **Evaluation:** This statement is correct. Blue-green algae (cyanobacteria) contain chlorophyll A, which is essential for photosynthesis, similar to higher plants.

**Hint:** Check if the pigment mentioned is common in both blue-green algae and higher plants.

### Step 2: Analyze the Second Statement
**Statement:** Blue-green algae may be filamentous, colonial, or unicellular.
- **Evaluation:** This statement is also correct. Blue-green algae can exist in various forms, including filamentous structures, colonies, or as individual unicellular organisms.

**Hint:** Consider the different forms of life that algae can take.

### Step 3: Analyze the Third Statement
**Statement:** Blue-green algae have heterocysts, which are clear cells without chlorophyll.
- **Evaluation:** This statement is correct. Heterocysts are specialized cells in some blue-green algae that lack chlorophyll and are involved in nitrogen fixation.

**Hint:** Recall the function of heterocysts and their role in nitrogen fixation.

### Step 4: Analyze the Fourth Statement
**Statement:** Blue-green algae are the connecting link between plants and animals.
- **Evaluation:** This statement is incorrect. Blue-green algae are not considered a connecting link between plants and animals. They are classified as prokaryotic organisms and are more closely related to bacteria than to plants or animals.

**Hint:** Think about the classification of organisms and the evolutionary relationships between them.

### Conclusion
After evaluating all four statements, the only incorrect statement is the fourth one. Therefore, the answer to the question is:

**Answer:** The incorrect statement is option number 4: "They are connecting link between plants and animals."