Download a) flowering plants

UNIT 2: PLANTS
Science 5th
Plants have three parts:
- The roots: they are in the soil. They absorb from the soil water and other substances.
- The stem: it supports the leaves. Water and nutrients are transported from the roots to the leaves
inside the stem.
- The leaves: they breathe and make the plant’s food.
I) PLANT GROUPS
A) FLOWERING PLANTS
This is the biggest group of plants. They are classified into:
 Gymnosperms: they have small flowers, but not fruit. Almost all gymnosperms are trees, like pine
trees.
 Angiosperms: they have flowers and fruit, such as chestnut trees or olive trees.
B) NON-FLOWERING PLANTS
This is the smallest group of plants. They need shade and moisture. They are classified into:
 Mosses: they are small plants which live on rocks, trees and the ground.
 Ferns: they are larger than mosses. They have thick, underground stems and big leaves.
II) PLANT NUTRITION
A) RESPIRATION
Plants take oxygen from the air, and release carbon dioxide. This
exchange of gases is called respiration. It takes place in leaves
continually, day and night.
B) NUTRITION
Plants are autotrophs: they make their own food. To make food,
plants need sunlight, carbon dioxide, water and minerals from the soil.
C) WATER AND MINERALS
Water and minerals are important for plant nutrition. In the soil,
minerals dissolve in water. Plants absorve this water through their
roots. These nutrients, called raw sap, travel up the stem to the
leaves.
D) PHOTOSYNTHESIS
Photosynthesis is the process through which plants make food from
sunlight, carbon dioxide, water and minerals, and release oxygen.
It takes place in the leaves, where raw sap mixes with carbon
dioxide and becomes elaborated sap. This is the plant’s food.
Photosynthesis only takes place during the day, because sunlight is
essential.
III) PLANT REPRODUCTION
There are two types of plant reproduction:
A) SEXUAL REPRODUCTION
Flowers are the reproductive organs of the plant. They have
two main parts:
 The stamens are the male parts which produce pollen.
 The ovary is the female part which contains ovules.
Ovules become seeds.
1.- POLLINATION
Tiny pollen grains form on the stamens. Pollination is the
movement of pollen from the stamens to the ovary.
Pollination usually takes place in the same plant. However, wind
and insects also carry pollen to other plants.
2.- FRUIT AND SEEDS
After pollination, the flower changes. Its petals fall. The ovary grows
and becomes a fruit with seeds inside. When the fruit is ripe, it falls to the ground. The fruit opens
and its seeds fall out.
3.- GERMINATION
Seeds germinate: they open and small roots and tiny leaves grow. A new plant forms.
B) ASEXUAL REPRODUCTION
Some plants reproduce without flowers or seeds:
 By tubers, such as potatoes. They are underground stems. These underground stems
develop roots. A thin stem rises above the ground and develop leaves. A complete plant
grows.
 By bulbs, such as onions. They also grow underground.
 By stolons, such as strawberry plants. Stolons are stems which extend across the ground.
Roots grow and a new plant begins.