OnlyGyaani • Class 7 Learning

Class 7 – Science

Explore 30 Class 7 Science topics covering plant and animal tissues, reproduction in flowering plants, human adolescence and hormones, cellular respiration, acids and bases, pH, weather and climate, atmospheric processes, food webs and ecological balance.

🌿 Plant and Animal Tissues

Plant Tissue Systems

Plant tissues are groups of cells organised to perform particular functions. Major tissue systems include the dermal, ground and vascular tissue systems.

Example:
Vascular tissues such as xylem and phloem help transport materials through different parts of a plant.

Practice:
Name the three major tissue systems found in plants.

Remember:
Different plant tissues work together to support growth, protection, transport and other plant functions.

Animal Tissue Systems

Animals contain specialised tissues composed of cells adapted to perform particular functions. Four major animal tissue types are epithelial, connective, muscular and nervous tissue.

Examples:
Muscle tissue produces movement, while nervous tissue helps transmit electrical and chemical signals.

Question:
Which animal tissue is mainly responsible for movement?

Remember:
Specialised tissues combine to form organs and organ systems.

Meristematic Tissues in Plants

Meristematic tissues contain actively dividing cells and are important for plant growth. They occur in regions such as the tips of roots and shoots and, in many plants, in lateral growth regions.

Example:
Apical meristems at root and shoot tips contribute to an increase in plant length.

Question:
Why are meristematic tissues important for growing plants?

Remember:
Meristematic cells retain the ability to divide actively.

Permanent Tissues in Plants

Permanent tissues are formed when cells produced by meristems differentiate and become specialised for particular functions. Examples include parenchyma, collenchyma, sclerenchyma, xylem and phloem.

Example:
Sclerenchyma cells can provide mechanical strength, while parenchyma may perform storage or photosynthetic functions.

Compare:
State one basic difference between meristematic and permanent tissues.

Remember:
Differentiation allows plant cells to become specialised for particular roles.

🌸 Reproduction in Flowering Plants

Structure of a Flower

A flower is the reproductive structure of flowering plants. Typical floral parts include sepals, petals, stamens and carpels. Different flowers may vary considerably in structure.

Important Parts:
Stamen → Anther + Filament
Carpel/Pistil → Stigma + Style + Ovary

Activity:
Draw a simple flower and label the stigma, style, ovary, anther, filament, petal and sepal.

Remember:
Pollen grains develop in the anthers, while ovules are located inside the ovary.

Sexual Reproduction in Flowering Plants

Sexual reproduction in flowering plants involves the production and fusion of male and female gametes. Pollination brings pollen to a receptive stigma, and subsequent processes can lead to fertilisation and seed formation.

Sequence:
Flower formation → Pollination → Fertilisation → Seed development

Question:
What is the key feature that makes reproduction sexual?

Remember:
Sexual reproduction involves fusion of gametes.

Pollination Mechanisms

Pollination is the transfer of pollen from an anther to a receptive stigma. Pollen may be transported by wind, water or animals such as insects, birds and other pollinators.

Example:
A bee visiting a flower may pick up pollen and transfer some of it to the stigma of another flower.

Think:
Why are brightly coloured petals and nectar useful to many insect-pollinated flowers?

Remember:
Pollination and fertilisation are different processes.

Fertilisation in Flowering Plants

After compatible pollen reaches the stigma, a pollen tube can grow through the style toward an ovule. Male gametes travel through the tube, allowing fertilisation to occur within the ovule.

Simplified Sequence:
Pollen lands on stigma → Pollen tube develops → Male gamete reaches ovule → Fertilisation

Question:
What structure carries male gametes toward the ovule?

Remember:
Fertilisation involves the fusion of male and female gametes.

Development of Fruits and Seeds

Following fertilisation in flowering plants, ovules generally develop into seeds. The ovary commonly develops into a fruit, although other floral tissues can also contribute to fruit formation in some species.

Basic Relationship:
Ovule → Seed
Ovary → Fruit

Question:
Which flower structure normally contains the ovules before fertilisation?

Remember:
Seeds contain the young plant embryo and stored or accessible nutritional resources for early development.

Methods of Seed Dispersal

Seed dispersal moves seeds away from the parent plant. Seeds and fruits may be dispersed by wind, water, animals, gravity or explosive mechanisms.

Examples:
Dandelion → Wind
Coconut → Water
Burrs → Animals

Think:
How can dispersing seeds away from the parent plant reduce competition?

Remember:
Seed structure often reflects its method of dispersal.

Vegetative Propagation

Vegetative propagation is a form of asexual reproduction in which new plants develop from vegetative parts such as stems, roots or leaves rather than from sexually produced seeds.

Examples:
Potato → Stem tuber
Ginger → Rhizome
Strawberry → Runner

Question:
Why is vegetative propagation classified as asexual reproduction?

Remember:
Vegetative offspring usually inherit essentially the same genetic information as the parent, apart from mutations.

🧬 Human Reproduction, Adolescence and Hormones

Human Reproductive Organs

The human reproductive system contains specialised organs involved in producing gametes and supporting reproduction. Male reproductive organs include the testes, while female reproductive organs include the ovaries, uterine tubes, uterus and vagina.

Key Functions:
Testes → produce sperm and secrete sex hormones
Ovaries → produce ova and secrete sex hormones
Uterus → supports development during pregnancy

Practice:
Match testes, ovaries and uterus with their basic reproductive functions.

Remember:
Sperm and ova are the male and female gametes respectively.

Biological Changes During Adolescence

Adolescence is a developmental period during which the body undergoes physical and reproductive maturation. Puberty involves hormonal changes that produce primary and secondary sexual characteristics.

Examples:
Changes can include growth spurts, body-hair development, changes in body composition and maturation of the reproductive system.

Think:
Why can the timing of puberty differ between individuals?

Remember:
The timing and rate of adolescent development naturally vary between individuals.

Endocrine Glands and Hormones

Endocrine glands release hormones into the bloodstream. Hormones act as chemical messengers and help regulate processes such as growth, metabolism, reproduction and responses to changing conditions.

Examples:
Pituitary gland → releases several regulatory hormones
Thyroid gland → produces thyroid hormones
Pancreas → produces hormones including insulin

Question:
How do hormones travel from endocrine glands to target tissues?

Remember:
Endocrine glands are ductless glands that release hormones into the internal circulation.

⚡ Cellular Respiration

Cellular Respiration

Cellular respiration consists of chemical processes through which cells release usable energy from nutrients such as glucose and capture part of that energy in ATP.

Example:
Cells use energy released through respiration for processes such as active transport, movement, growth, repair and synthesis.

Question:
Why do living cells need a continuous supply of usable energy?

Remember:
Breathing brings gases into and out of the body; cellular respiration is a set of chemical reactions occurring within cells.

Aerobic Respiration

Aerobic respiration uses oxygen and can release a large amount of usable energy from glucose. In eukaryotic cells, important stages of aerobic respiration occur in mitochondria.

Overall Relationship:
Glucose + Oxygen → Carbon dioxide + Water + Energy

Practice:
Identify the main reactants and products in the overall aerobic respiration relationship.

Remember:
Aerobic respiration requires oxygen.

Anaerobic Respiration

Cells can obtain some energy from glucose without using oxygen. These anaerobic pathways yield much less usable energy per glucose molecule than aerobic respiration.

Example:
Yeast can carry out alcoholic fermentation, producing ethanol and carbon dioxide when oxygen is limited.

Compare:
What is the key difference between aerobic and anaerobic energy release in relation to oxygen?

Remember:
Anaerobic pathways do not require oxygen and yield less ATP per glucose than aerobic respiration.

🧪 Acids, Bases, Indicators and pH

Acids and Their Chemical Characteristics

Acids are substances that produce hydronium ions in aqueous solution. They have characteristic reactions and generally have pH values below 7 under ordinary introductory conditions.

Examples:
Hydrochloric acid, sulfuric acid and acetic acid are familiar acids. Lemon juice contains naturally occurring acids such as citric acid.

Question:
What happens to blue litmus paper in an acidic solution?

Remember:
Never identify laboratory acids by tasting them.

Bases and Their Chemical Characteristics

Bases can accept protons or produce hydroxide ions in aqueous solutions, depending on the chemical definition being used. Basic solutions generally have pH values above 7 at ordinary classroom conditions.

Examples:
Sodium hydroxide and calcium hydroxide are common bases. Some household substances also form mildly basic solutions.

Question:
What happens to red litmus paper in a basic solution?

Remember:
Strong bases can be corrosive and must be handled safely.

Natural and Synthetic Indicators

Indicators are substances that show characteristic changes, often in colour, depending on the acidity or basicity of a solution. Indicators may be obtained from natural sources or manufactured.

Examples:
Litmus → natural-origin indicator
Turmeric → natural indicator
Phenolphthalein → synthetic indicator

Activity:
Create a table showing how red and blue litmus behave in acidic and basic solutions.

Remember:
Different indicators change over different pH ranges.

Understanding the pH Scale

The pH scale describes the acidity or basicity of an aqueous solution. At about 25°C, a neutral solution has a pH of 7. Values below 7 are acidic and values above 7 are basic.

Basic Interpretation:
pH below 7 → Acidic
pH 7 → Neutral at about 25°C
pH above 7 → Basic

Practice:
Classify solutions with pH 3, pH 7 and pH 10 as acidic, neutral or basic.

Remember:
The pH scale is logarithmic, so a change of one pH unit represents a tenfold change in hydronium-ion concentration.

Neutralisation and Its Applications

Neutralisation is a reaction between an acid and a base. In a common acid-hydroxide reaction, salt and water are formed.

General Pattern:
Acid + Base → Salt + Water

Think:
Why can controlled neutralisation be useful when treating acidic or basic materials?

Remember:
Neutralisation does not always mean that equal volumes of two solutions will produce pH 7; the quantities and strengths involved matter.

🌦️ Weather, Climate and Atmospheric Processes

Weather Elements and Their Measurement

Weather describes atmospheric conditions at a particular place and time. Scientists measure several elements to describe and predict weather.

Weather Elements:
Temperature → Thermometer
Air pressure → Barometer
Wind speed → Anemometer
Rainfall → Rain gauge
Humidity → Hygrometer

Practice:
Match thermometer, barometer, anemometer and rain gauge with the weather element each measures.

Remember:
Weather observations are most useful when measurements are taken systematically.

Difference Between Weather and Climate

Weather refers to short-term atmospheric conditions. Climate describes the long-term patterns and statistical characteristics of weather in a region, usually considered over decades.

Example:
“It is raining today” describes weather.
“A region generally has hot, dry summers” describes a climatic pattern.

Question:
Why cannot one unusually cold day by itself define the climate of a region?

Remember:
Weather changes over short periods; climate describes longer-term patterns.

Formation of Atmospheric Winds

Winds are movements of air produced largely by differences in atmospheric pressure. Uneven heating of Earth’s surface contributes to temperature and pressure differences that drive air movement.

Example:
Local differences in heating between land and water can contribute to sea breezes and land breezes.

Think:
How can unequal heating of Earth’s surface lead to air movement?

Remember:
Air tends to move from areas of higher pressure toward areas of lower pressure, while Earth’s rotation and other factors influence actual wind patterns.

Cloud Formation

Clouds form when moist air cools sufficiently for water vapour to condense onto tiny particles in the atmosphere, producing small water droplets or ice crystals.

Simplified Process:
Moist air rises → Air cools → Water vapour condenses → Cloud droplets or ice crystals form

Question:
Why is cooling important in the formation of many clouds?

Remember:
Clouds consist mainly of tiny liquid water droplets, ice crystals, or a mixture of both.

Precipitation and Its Forms

Precipitation occurs when water particles or ice particles in clouds grow large enough to fall through the atmosphere and reach the ground.

Forms of Precipitation:
Rain • Snow • Sleet/Ice Pellets • Hail

Question:
How can atmospheric temperature affect whether precipitation reaches the ground as rain or snow?

Remember:
The form of precipitation depends on atmospheric conditions, especially temperature.

🌍 Ecosystems and Ecological Balance

Producers, Consumers and Decomposers

Organisms in ecosystems can be described according to how they obtain energy and nutrients. Producers make organic matter, consumers obtain energy by feeding on other organisms, and decomposers break down dead organic material and wastes.

Examples:
Grass → Producer
Deer → Consumer
Many fungi and bacteria → Decomposers

Practice:
Classify grass, rabbit, hawk and a decomposer fungus according to their ecological roles.

Remember:
Decomposers play an important role in returning nutrients to ecosystem nutrient cycles.

Energy Transfer Through Food Webs

A food web represents interconnected feeding relationships in an ecosystem. Energy enters many ecosystems through producers and is transferred to consumers through feeding.

Simple Food Chain:
Grass → Grasshopper → Frog → Snake

Activity:
Create a small food web using grass, seeds, grasshopper, rabbit, frog, snake and hawk.

Remember:
Arrows in food chains and food webs conventionally show the direction of energy transfer—from the organism being eaten toward the consumer.

Ecological Balance in Natural Systems

Ecosystems are dynamic systems in which populations, resources and environmental conditions interact. Ecological stability depends on many relationships rather than on every population remaining at a fixed number.

Example:
A major decline in a predator, pollinator or producer population can cause changes in several other populations within a food web.

Think:
Predict two possible effects if producers in an ecosystem were greatly reduced.

Remember:
Biodiversity, resource availability, species interactions and environmental conditions all contribute to ecosystem functioning and resilience.