23 Growth and development (Extension) 23.1 Growth and development 23.2 Growth and development in humans 23.3 Seed germination 23.4 Growth and development in plants 23.5 Measurement of growth Mind Map

23.1 Growth and development

1. What is Growth ? A permanent increase in Size Weight Increase in complexity 2. What is Development ? By cell elongation 2 By cell division 1 By cell differentiation Growth and development

After fertilisation Zygote undergoes mitosis Size & weight Growth 23.1 Growth and development

cells undergo differentiation Other cells Complexity Development Different types of cells are formed 23.1 Growth and development

23.2 Growth and development in humans & in

First two years after birth, growth rate is very fast Growth curve of humans age (years) height (cm) birth 23.2 Growth and development in humans

Age 3 to 12, growth rate slows down Growth curve of humans age (years) height (cm) birth 23.2 Growth and development in humans

Age 13 to 17, growth rate is fast again Growth curve of humans age (years) height (cm) birth 23.2 Growth and development in humans

Growth rate stops at about 20 Growth curve of humans age (years) height (cm) birth 23.2 Growth and development in humans

Relative growth (%) Age (years) head & brain whole body reproductive organs Relative growth rates of different parts of the body Different parts of the body grow at different rates Grow rapidly in the first three years and then slow down 23.2 Growth and development in humans

Relative growth (%) Age (years) head & brain whole body reproductive organs Relative growth rates of different parts of the body The last organs to develop and differentiate 23.2 Growth and development in humans Different parts of the body grow at different rates

2 months (foetal) 5 months (foetal) newborn 2 years 6 years 12 years 25 years 23.2 Growth and development in humans

The growth rates of boys and girls Body weight (kg) Age (years) boys girls Between ages of 11 & 14 growth rate is faster in girls than in boys After age 14 growth rate is faster in boys than in girls 23.2 Growth and development in humans

23.3 Seed germination

When a seed starts to germinate Fresh mass increases ∵ it absorbs water from the soil

However, the dry mass of the seed decreases 23.3 Seed germination Make new protein molecules for cell membrane and cytoplasm The stored protein is broken down into amino acid and is used to Make new cell walls Release energy in respiration The stored starch is broken down into sugar and is used to

But… Once the plumule appears above the soil the young leaves appear and carry out photosynthesis If the rate of photosynthesis is faster than that of respiration the dry mass increases 23.3 Seed germination

WaterWarmthOxygen Conditions for seed germination 23.3 Seed germination

Water Softens the seed coat Activates the enzymes to break down the stored food Dissolves food Transports dissolved food to the growing point of embryo Conditions for seed germination 23.3 Seed germination

Warmth Enzymes work at a faster rate at higher temperature Conditions for seed germination 23.3 Seed germination

Oxygen Enables seeds to respire aerobically to supply energy for growth Conditions for seed germination 23.3 Seed germination

1.You are given some mung bean seeds. Design and perform investigations to study the conditions necessary for seed germination. 2.Bring your proposal to your teacher for perusal. 3.You can carry out the investigation with the permission of your teacher. 4.What conclusion can you draw after the experiment? Experiment 23.1 To study seed germination 23.3 Seed germination

23.4 Growth and development in plants & in

Growth & development at root tips phloem xylem region of root hairs region of cell differentiation region of cell elongation region of cell division root cap protects the root as it grows through the soil 23.4 Growth and development in plants

Growth & development at root tips Growing point Cell undergoes mitosis to produce small new cells 23.4 Growth and development in plants

Growth & development at root tips Growing point 23.4 Growth and development in plants Cells absorb water & expand / elongate Vacuolation helps the roots to push their way down into the soil

Growth & development at root tips 23.4 Growth and development in plants Region of differentiation The cell wall becomes thickened & the cells differentiate into specialised tissues e.g. cortex, xylem, phloem & cambium

Root cap Growing point 23.4 Growth and development in plants Growth & development at root tips

Growth & development at shoot tips Shoots grow in a way similar to the roots Growing point (apical meristem) 23.4 Growth and development in plants

1.Germinate some broad bean seeds by planting them in moist peat with their radicle pockets positioned deliberately so that their radicles will emerge and grow directly downwards. Leave them until their radicles (young roots) have grown to about 3cm long. 2.Choose 3 broad bean seedlings with straight radicles. Rinse the seedlings and blot their radicles thoroughly with tissue paper. Experiment 23.2 To study the growth of young seedlings 23.4 Growth and development in plants

3.Using Indian ink, mark the terminal 2 cm of the radicles at 2 mm intervals. 4.Carefully place the broad bean seedlings in a beaker or glass jar as shown below. wire thread (used to mark the radicle with Indian ink) blotting paper (or newspaper) glass jar broad bean seedling water 23.4 Growth and development in plants Experiment 23.2 To study the growth of young seedlings

5.Leave the seedlings for several days. Examine them again Growth and development in plants Experiment 23.2 To study the growth of young seedlings wire thread (used to mark the radicle with Indian ink) blotting paper (or newspaper) glass jar broad bean seedling water

Question 1: Do all parts of the radicle grow? Answer: Growth occurs only in the regions just behind the tip. No growth occurs in the very tip as it is covered by the root cap. radicle plumule 23.4 Growth and development in plants Experiment 23.2 To study the growth of young seedlings

Question 2: Which region shows the greatest growth rate? Answer: The region of maximum growth is the region of elongation which is located immediately behind the tip. radicle plumule 23.4 Growth and development in plants Experiment 23.2 To study the growth of young seedlings

23.4 Growth and development in plants

Dry mass (g) Time (weeks) germination Food reserves are used for respiration & no food formation because of no leaf Thus, it shows a negative growth 23.4 Growth and development in plants

Dry mass (g) Time (weeks) germination Once the green leaves undergo photosynthesis & the rate of photosynthesis is higher than that of respiration It shows a positive growth 23.4 Growth and development in plants

Dry mass (g) Time (weeks) germination After 20 weeks, there is a sudden decrease in dry mass Due to dispersal of fruits & seeds 23.4 Growth and development in plants Finally the plant dies

Dry mass (g) Time (weeks) germination Only the food reserves are used Rate of photosynthesis is higher than that of respiration Dispersal of fruits & seeds & finally the plant dies Summary 23.4 Growth and development in plants

23.5 Measurement of growth

Size Fresh mass Dry mass 23.5 Measurement of growth

Size e.g. height, length, surface area and volume AdvantagesDisadvantage Does not damage the organisms Quick & easy to carry out Does not take into account of growth in other dimensions 23.5 Measurement of growth

Total mass of an organism including the water content inside its body AdvantagesDisadvantages Usually does no harm to the organism A quick and simple way May kill the large plant because it is necessary to uproot it Fresh mass The result will vary depending on the amount of water taken in or lost 23.5 Measurement of growth

Total mass of an organism excluding water Advantage Disadvantages The most accurate method The organism is killed Have to use a large number of organisms Dry mass A time-consuming method Impossible for large organisms 23.5 Measurement of growth

Mind Map Growth permanent increase in 1. size Development 2. weight 1. cell division 2. cell elongation by vacuolation in plants mitosis 1. size 2. fresh mass 3. dry mass by processes include measurements include increase in by produce complexity differentiation different kinds of cells