Question

PLEASE HELP WITH ALL QUESTIONS

QUESTION 1 Distinguish or explain the difference between the following: 1.1 Primary and secondary growth 1.2 Heartwood and sapwood 1.3 Simple and multiple fruits 1.4 Bottleneck effect and genetic effect QUESTION 2 2.1 Distinguish between annual, biennial and perennial plants. 2.2 Provide THREE examples of ways that humans use roots. 2.3 Is the following structures a root, stem or leaf and what is its function? a. Haustoria b. Rhizome c. Stipule spine (3 x 2 = 6) 2.4 Briefly discuss THREE major types of sexual life cycles. 2.5 Describe some of the benefits that stems provide to plants. QUESTION 3 3.1 Describe the structure and function of five types of modified leaves. 3.2 Describe the three tissue systems that exist in leaves, stem and roots, in terms of cell types and functions. QUESTION 4 4.1 Name and discuss THREE main types of natural selection. 4.2 What is an herbarium? Why is it important?

Answer 1

1.1) Primary Growth: It is the growth due to the division of primary meristems such as apical meristem and intercalary meristem. It helps in increasing the length of the stem or root.

Secondary Growth: It is the growth due to the division of secondary meristem or lateral meristem such as cork cambium and vascular cambium. It helps in increasing the girth of stem or root.

1.2) Heartwood: It is also called as 'Duramen'. It is the secondary xylem found at the center of the stem of old trees. It is dark in colour and consists of dead lignified xylary elements due to the accumulation of substances like resins, oils, tannins, pigments etc. Due to this, the heartwood is resistant to infections by pathogens and pest attack. It also provides mechanical support to the tree. It does not transport water and minerals.

Sapwood: It is also called as 'Alburnum'. It is the secondary xylem found at the peripheral region of the stem of old trees. It is light in colour and it consists of live xylary elements. It is not durable like the heartwood. It is more susceptible to infections and pest attack. Sapwood takes part in transport of water and minerals.

1.3) Simple fruit: It is the fruit developed from a single ovary of a single flower. Example- Mango

Multiple fruit: It is the fruit developed from multiple flowers of an inflorescence. It is also called 'composite fruit'. Example- Jackfruit.

1.4) Bottleneck effect: It is a phenomenon where majority of individuals of a population die which results in a drastic reduction of population size. The death may be due to natural disaster or human interference.The surviving individuals form a new population. The reduction in genetic variance results in formation of new species.

Genetic effect: It is founder effect. It is a phenomenon in which a small population of individuals that has got isolated or drifted from the original parent population forms a new population of individuals. This new population will result in formation of new species.