Key Concepts in Biology: Life Processes and Reproduction

MRS GREN

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Biology

The study of life — from cells to whole ecosystems.

Respiration

A process where organisms extract energy from glucose.

Excretion

Removal of metabolic waste (like urea or CO₂).

Difference between excretion and egestion

Excretion removes waste made by cells; egestion removes undigested food.

Eukaryotic cell

A cell with a nucleus and membrane-bound organelles.

Prokaryotic cell

A cell without a nucleus; e.g. bacteria.

Eukaryotic kingdoms

Animalia, Plantae, Fungi, Protista.

Prokaryotic kingdoms

Bacteria and Archaea.

Size of eukaryotic vs prokaryotic cells

Eukaryotic ~50μm, Prokaryotic ~1μm.

Magnification formula

Image size ÷ Actual size.

Asexual reproduction

One parent produces genetically identical offspring.

Bacterial reproduction

By binary fission — a type of asexual reproduction.

Yeast reproduction

By budding — a form of asexual reproduction.

Sexual reproduction

Two parents produce genetically varied offspring.

Zygote

A fertilised egg formed when sperm and egg fuse.

Cell specialisation

When cells develop specific roles (e.g. nerve cells).

Stem cell

An undifferentiated cell that can become specialised.

Differentiation

The process of becoming specialised.

Tissue

A group of similar cells doing the same job.

Organ

A structure made of tissues with a specific function.

Organ system

A group of organs working together.

Organism

A living thing made of organ systems.

Autotroph

An organism that makes its own food (e.g. plants).

Heterotroph

An organism that consumes others for food (e.g. animals).

Balanced equation for photosynthesis

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.

Photosynthesis location

In chloroplasts using chlorophyll.

Light colours increasing photosynthesis

Red and blue (green is reflected).

Greenhouse effect on photosynthesis

More light, warmth and CO₂ increases glucose production.

Uses of glucose in plants

Making starch, cellulose, energy (respiration), proteins and lipids.

Mineral absorption in plants

Through roots — potassium, phosphate, magnesium, etc.

Word equation for aerobic respiration

Glucose + Oxygen → Carbon dioxide + Water.

Aerobic respiration location

In the mitochondria.

Anaerobic respiration (animals)

Glucose → Lactic acid.

Anaerobic respiration (yeast)

Glucose → Alcohol + Carbon dioxide.

Aerobic vs anaerobic respiration

Aerobic releases more energy (ATP).

Function of the digestive system

Breaks down food and absorbs nutrients.

Mouth function

Starts digestion by chewing and mixing food with saliva.

Stomach function

Uses acid and enzymes to break food down.

Small intestine function

Absorbs nutrients into the blood.

Liver function

Produces bile to help digest fats.

Gallbladder function

Stores bile and releases it into the intestine.

Pancreas function

Makes enzymes: amylase, protease, lipase.

Large intestine function

Absorbs water and forms faeces.

Enzyme

A biological catalyst that speeds up reactions.

Catalyst

A substance that speeds up a reaction without being used.

Active site

The part of the enzyme that binds to the substrate.

Amylase

An enzyme that breaks down carbohydrates into simple sugars.

Protease

An enzyme (e.g. pepsin) that breaks down proteins into amino acids.

Lipase

Enzyme that breaks down lipids into fatty acids and glycerol.

Nuclease

Enzyme that breaks down nucleic acids into nucleotides.

Test for starch

Iodine turns blue-black if present.

Test for glucose

Benedict's + heat turns red/orange if present.

Test for protein

Biuret test turns purple if present.

Test for lipids

Ethanol test produces cloudy white emulsion if present.

Stamen

Male parts of a flower, consisting of anther and filament.

Carpel

Female parts of a flower, consisting of stigma, style, and ovary.

Anther

Produces pollen (male gametes).

Stigma

Collects pollen.

Ovary

Contains ovules (egg cells).

Pollination

Transfer of pollen from anther to stigma.

Fertilisation in plants

Occurs in the ovary, when pollen fuses with an ovule.

Testes

Produce sperm and testosterone; site of meiosis.

Scrotum

Protects testes and controls temperature.

Urethra (male)

Transports urine and semen out of the body.

Epididymis

Stores, matures, and moves sperm.

Prostate gland

Adds fluid to form semen.

Seminal vesicle

Adds nutrient-rich fluid to semen.

Ejaculatory duct

Delivers sperm into the urethra during ejaculation.

Vas deferens

Transports sperm from testes to urethra.

Penis

Transfers semen into the vagina.

Sperm duct

Connects testes to urethra through the prostate.

Cervix

Narrow opening between uterus and vagina; allows fluid flow.

Vagina

Birth canal; receives sperm during intercourse.

Uterus

Where a fertilised egg implants and baby develops.

Ovaries

Produce eggs and hormones (oestrogen and progesterone).

Oviducts

Transport eggs to the uterus; site of fertilisation.

Fundus

Top of uterus; supports pregnancy and hormone control.

Endometrium

The uterus lining that thickens and sheds monthly.

Ovulation

Release of an egg from the ovary (around day 14).

Menstrual cycle

~28-day cycle preparing uterus for pregnancy.

Oestrogen

Builds the uterus lining during the cycle.

Progesterone

Maintains the uterus lining after ovulation.

Implantation

When a fertilised egg embeds into the uterine wall.

Gestation

Time between fertilisation and birth (~9 months).

Placenta

Transfers oxygen/nutrients to the fetus; removes waste.

Puberty

The time when the body develops to become reproductive.

Testosterone

Hormone that causes puberty in boys.

Oestrogen (girls)

Hormone that causes puberty in girls.

Changes in boys during puberty

Voice deepens, facial hair, sperm production, muscle growth.

Changes in girls during puberty

Breasts grow, hips widen, periods start, body hair.

Seminal fluid

Fluid that nourishes and helps sperm move.

Semen

A mixture of sperm cells and seminal fluid.

Condom

Barrier that prevents sperm from entering; protects against STIs.

Combined pill

Prevents ovulation and thickens cervical mucus.

IUD

Placed in uterus; prevents implantation of a fertilised egg.

Diaphragm

A barrier that covers the cervix and stops sperm entering.

Vasectomy

Sperm ducts are cut or sealed to prevent sperm release.

Continuous variation

Traits that vary on a scale (e.g. height, weight).

Discontinuous variation

Traits with distinct groups (e.g. blood group).