Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Identify main plant and animal tissues and relate their structure to function.
• Explain the characteristics and roles of different plant tissues.
• Explain the characteristics and roles of different animal tissues.
• Compare and contrast different types of epithelial tissue.
• Describe the various types of connective tissue and their functions.

Lesson summary

This week, we will revisit and extend our understanding of plant and animal tissues. This topic is crucial because understanding the structure and function of these tissues provides the foundation for comprehending how multicellular organisms work. In the South African context, understanding plant tissues can inform agricultural practices for improved crop yields and understanding animal tissues is vital for understanding animal health, which is critical for both commercial farming and subsistence farming communities.

Furthermore, understanding how diseases affect tissues is relevant to understanding and preventing disease in humans and livestock.

Lesson notes

Plant Tissues Plant tissues are broadly categorized into: Meristematic Tissue: This is the tissue responsible for plant growth. It consists of undifferentiated cells capable of cell division.

There are two main types: Apical meristems:* Found at the tips of roots and shoots, responsible for primary growth (increase in length). This is particularly relevant in South Africa regarding staple crops like maize, where increased shoot length can affect yield. Lateral meristems (vascular cambium and cork cambium):* Responsible for secondary growth (increase in girth or thickness). This is crucial for understanding the growth of indigenous trees like the Marula, which is important culturally and economically.

Permanent Tissues: These tissues are derived from meristematic tissues and have differentiated to perform specific functions.

Parenchyma:* The most abundant tissue, found in leaves, stems, and roots. Parenchyma cells are thin-walled and perform various functions such as photosynthesis, storage, and secretion.

Example: The fleshy part of a fruit like a mango consists mainly of parenchyma tissue.

Collenchyma:* Provides flexible support to young stems and leaves. Collenchyma cells have thickened cell walls at the corners.

Example: The strings you find in celery are collenchyma.

Sclerenchyma:* Provides rigid support to the plant. Sclerenchyma cells have thick, lignified cell walls and are often dead at maturity.

Example: The hard shell of a walnut.

Xylem:* A vascular tissue that transports water and minerals from the roots to the rest of the plant. Xylem cells are dead and form hollow tubes. Water movement relies on cohesion and adhesion. The importance of efficient water transport is amplified in arid regions of South Africa.

Phloem:* A vascular tissue that transports sugars (produced during photosynthesis) from the leaves to other parts of the plant. Phloem cells are living but have sieve plates that allow for the passage of sugars.

Epidermis:* The outer protective layer of the plant. It is often covered with a waxy cuticle to prevent water loss. This is especially important for plants in drier climates of the country.