How do Organisms Reproduce? · Class 10 Science: 66 flashcards

No — it consumes energy and gives the individual no survival benefit. It persists because it maintains the SPECIES: populations that reproduce continue across generations; those that don't disappear.

The copying (replication) of DNA — the cell duplicates its blueprint and creates additional cellular machinery, then divides so each daughter cell receives a DNA copy.

Small errors inevitably occur during copying. Drastic ones are fatal, but survivable errors create VARIATIONS — differences between offspring and parents — which allow species to adapt to changing environments and drive evolution.

In an identical population, a harmful change (heat, disease) can kill everyone. In a varied population, some individuals usually carry traits that let them survive and repopulate — variation is species-level insurance.

The Amoeba's nucleus divides first, then the cytoplasm splits, producing two daughter cells. Having no fixed shape, Amoeba can divide in ANY plane.

Leishmania has a whip-like flagellum at one end, so its binary fission occurs in a DEFINITE plane relative to that structure — unlike shapeless Amoeba's any-plane split.

Division of one cell into MANY daughter cells simultaneously. Plasmodium — the malaria parasite — reproduces this way inside the human body.

A simple multicellular organism breaking into pieces, each of which grows into a new individual — shown by the filamentous alga Spirogyra.

Complex organisms have highly specialised, organised tissues and organs — a random piece lacks the full set and the organisation to rebuild it. Fragmentation works only where cell specialisation is minimal.

The regrowth of a complete organism from a cut body piece — specialised cells proliferate into a mass and then re-differentiate into ordered cell types. Hydra and Planaria are the classic examples.

Because it is a repair capability displayed only when the body happens to be cut — organisms do not normally depend on being fragmented to multiply; their routine reproduction uses other modes.

Repeated cell division at one site on the body produces an outgrowth — a bud — which develops into a miniature Hydra. When mature, it detaches from the parent and lives independently.

By budding: a small bud grows out from the parent cell, receives a nucleus copy, and pinches off as a new cell — sometimes chains of buds form under fast growth.

Asexual reproduction in plants where new individuals grow from vegetative organs — roots, stems or leaves — rather than seeds. Examples: potato tubers (stem), Bryophyllum leaves, rose/sugarcane stem cuttings.

Tiny plantlets — complete with roots — develop in the notches along its leaf margins; they drop off and grow into independent plants wherever they land on soil.

Each eye is a bud on the tuber (an underground stem); given soil and moisture, it sprouts shoots and roots — a whole new potato plant.

Cuttings (rooting cut stems — rose, sugarcane), layering (rooting a branch while attached, then separating it), and grafting (joining a chosen variety's shoot onto another plant's rootstock — mango, citrus).

(1) Faster — plants flower and fruit earlier than seed-grown ones; (2) offspring are genetically identical to the selected excellent parent; (3) it is the only way to propagate seedless varieties like banana, some oranges and jasmine.

The mould's upright hyphae carry sporangia — capsule-like structures containing hundreds of spores. Each spore has a thick protective wall; released into air, spores travel widely and germinate into new mould wherever they meet a moist surface (like damp bread).

Its thick wall — which shields it from drying and harsh conditions until it lands on a moist surface suitable for germination.

A single parent; no gametes or fusion; offspring produced relatively fast and in numbers; and offspring that are genetically (almost) identical to the parent — clones, with variation arising only from small DNA-copying errors.

All plants share the same strengths AND weaknesses — a single new disease or climate shift that beats one plant beats them all. Without variation, there are no differently-built survivors.

It combines DNA from two different parents, giving each offspring a new gene combination — on top of the copying-error variation both modes share. More variation means faster adaptation of the species.

If two full cells fused, the DNA amount would double every generation. Halving in the gametes ensures fusion restores exactly the normal amount — keeping the species' DNA quantity constant.

The male gamete is small and motile (built to travel); the female gamete is larger and carries the stored food for the early embryo.

Sepals — green, protect the bud; petals — coloured, attract pollinators; stamens — the male parts producing pollen; carpel (pistil) — the female part containing the ovules.

A stalk called the filament topped by the anther — the swollen head where pollen grains (carrying the male germ-cells) are produced.

Stigma — the sticky tip that receives pollen; style — the elongated stalk connecting downward; ovary — the swollen base containing ovules, each with an egg cell.

Unisexual flowers contain either stamens or carpel, not both — papaya, watermelon. Bisexual flowers contain both male and female parts — hibiscus, mustard.

The transfer of pollen from an anther to a stigma. Self-pollination: within the same flower or plant. Cross-pollination: from one plant to another — via wind, water, insects or other animals.

Wind, water, insects (bees, butterflies) and other animals (birds, bats).

Pollination only delivers pollen to the stigma — transport. Fertilisation is the actual fusion of the male germ-cell with the egg cell inside the ovule, which happens only after the pollen tube grows down and delivers it.

The pollen grain germinates, growing a pollen tube down through the style — guided chemotropically — until it reaches an ovule in the ovary. The male germ-cell moves down the tube and fuses with the egg cell, forming the zygote.

The single cell formed by fusion of the male germ-cell and egg cell at fertilisation. It divides repeatedly to become the embryo — the miniature future plant inside the developing seed.

The zygote develops into the embryo; the ovule matures into the seed (embryo + food + seed coat); the ovary swells and ripens into the fruit enclosing the seeds; petals, sepals, stamens, stigma and style generally shrivel and fall off.

The ripened ovary of a flower — the structure that develops from the ovary wall after fertilisation and encloses the seed or seeds.

The radicle (the future root), the plumule (the future shoot), and the cotyledons — the food-storing seed leaves that nourish early growth.

Water (to activate the embryo and soften the coat), air/oxygen (for respiration's energy), and suitable warmth. Light is generally not required at this stage.

The embryo resumes growth using the cotyledons' stored food: the radicle emerges first and grows downward as the root; the plumule then grows upward as the shoot; once green leaves open, photosynthesis takes over feeding the seedling.

As payment and advertisement for pollinators — insects and other animals visit for the nectar, get dusted with pollen, and carry it to the next flower. The immobile plant hires mobile couriers.

Self-pollination combines a plant's genes with its own — offspring stay close to the parent's type. Cross-pollination merges DNA of two DIFFERENT plants, producing genuinely new combinations in the offspring.

The juicy flesh is the ripened ovary wall (the fruit); the kernel inside the stone developed from the ovule — it is the seed, containing the embryo and its food store.

Papaya bears unisexual flowers, often with male and female flowers on separate plants — pollen must travel from a male tree to a female tree. A lone female tree without a pollen source nearby sets no fruit.

Chemotropism — chemical signals from the ovule's side steer the tube's growth down the style toward the egg, the same directional-growth principle seen in roots growing toward water.

The period when the reproductive tissues and body mature for reproduction — beginning around 10-12 years in girls and slightly later in boys, driven by testosterone (testes) and oestrogen (ovaries).

Growth spurt; hair growth in new regions (underarms, pubic area); oilier skin, often causing pimples; and general maturation of reproductive organs.

Boys: deepening of the voice, growth of facial hair (testosterone). Girls: breast development and the start of menstruation (oestrogen).

Because sperm formation requires a temperature about 1-3 °C LOWER than normal body temperature — the scrotum maintains that cooler environment.

Sperm (the male gametes) and the hormone testosterone — which regulates sperm production and drives the male changes of puberty.

Made in the testes → carried by the vas deferens → joined by fluids of the prostate and seminal vesicles (forming semen) → out through the urethra.

The fluid mixture of sperm plus secretions of the prostate and seminal vesicles. The fluid provides a transport medium and nourishment for the sperm on their journey.

A microscopic cell that is essentially a head packed with DNA, a midpiece supplying energy, and a long tail (flagellum) that propels it — a genetic delivery vehicle built to swim.

At birth the ovaries already hold thousands of IMMATURE eggs. From puberty onward, one egg matures and is released each month — the ovaries alternating — continuing until later life.

In the oviduct (fallopian tube) — the released egg is caught there, and sperm that swim up through the uterus meet it in the tube.

The muscular, elastic chamber where the embryo implants, is nourished via the placenta, and develops for about nine months until birth. Its lining thickens every month in preparation.

The embedding of the early embryo (which divided as it travelled from the oviduct) into the thickened, blood-rich lining of the uterus — the true start of pregnancy.

A disc-shaped tissue connecting the embryo to the uterine wall. Villi on the embryo's side project into blood spaces on the mother's side — creating a LARGE surface area for exchange, the same design principle as villi and alveoli.

It passes glucose, oxygen and other nutrients from the mother's blood to the embryo, and carries the embryo's wastes back into the mother's blood for her body to excrete — the embryo's lungs, gut and kidneys by proxy.

After about nine months of development, rhythmic contractions of the strong uterine muscles push the baby out through the cervix and vagina — the birth canal.

The egg survives about a day. The uterus's thickened lining, no longer needed, slowly breaks down and is shed through the vagina as blood and mucus — menstruation, lasting about 2-8 days and recurring roughly monthly.

Because it is normal, healthy physiology — simply the removal of an unused uterine preparation. What it genuinely calls for is hygiene, iron-rich nutrition and matter-of-fact support — not myths or restrictions.

Barrier — condoms; hormonal — oral pills (prevent egg release); intrauterine — IUCD/copper-T placed in the uterus; surgical — vasectomy (men) and tubectomy (women).

Condoms (barrier method) — they physically block the exchange of body fluids that transmits infections. All other methods act on eggs, hormones or tubes and do nothing to stop pathogen transfer.

Vasectomy blocks/cuts the vas deferens so semen carries no sperm; tubectomy blocks the oviducts so eggs cannot meet sperm. Neither affects hormone production, strength or general health — they alter fertility only.

Bacterial: gonorrhoea and syphilis. Viral: genital warts and HIV-AIDS.

Because it enabled sex-selective abortion of girls, measurably skewing child sex ratios. The ban (and its enforcement) protects both the legal principle of equality and society's demographic health.