Which of the following processes is used by Yeast to make alcohol?

Answer: Fermentation. Fermentation is the anaerobic process where sugars are converted into alcohol and CO₂ by yeast (Saccharomyces cerevisiae).

According to Lindeman's 10% law, if producers have 10,000 J, how much energy reaches the secondary consumer?

Answer: 100 J. Producer (10,000) → Primary (1,000) → Secondary (100 J). Energy is reduced by 90% at each step — only 10% passes through.

Which bacterium is responsible for nitrogen fixation in legume root nodules?

Answer: Rhizobium. Rhizobium bacteria live in symbiotic root nodules of legumes (pulses like peas, beans) and fix atmospheric nitrogen into ammonia, enriching soil fertility.

Answer: Less than 5.6. Normal rain has pH of 5.6 (slightly acidic due to CO₂). Acid rain has pH less than 5.6 due to dissolved SO₂ and NOₓ forming sulfuric and nitric acids.

Which book published by IUCN contains a list of endangered species?

Answer: Red Data Book. The Red Data Book (Red List) is published by IUCN (International Union for Conservation of Nature) and tracks the conservation status of all known species worldwide.

Lamarck's theory of acquired characters was disproved because:

Answer: Acquired characters are not encoded in DNA and cannot be inherited. Weismann showed that somatic (body) changes cannot be passed to germ cells. Only changes in DNA (genes) are heritable — acquired characters during lifetime are NOT inherited.

Which of the following is an example of mutualism?

Answer: Bee pollinating a flower. In mutualism, both species benefit (+/+). Bee gets nectar (food) and flower gets pollinated. Tapeworm = parasitism. Orchid on tree = commensalism. Lion-deer = predation.

In India, Project Tiger was launched in the year:

Answer: 1973. Project Tiger was launched in 1973 under the Wildlife Protection Act 1972, during the tenure of PM Indira Gandhi. It is India's most successful conservation initiative.

Which ecological pyramid is always upright?

Answer: Pyramid of Energy. Pyramid of Energy is ALWAYS upright because energy always decreases from one trophic level to the next (Lindeman's 10% rule). Numbers and biomass pyramids can be inverted (e.g., in parasitic chains).

The "Ozone layer" protects Earth from which harmful radiation?

Answer: Ultraviolet radiation. The ozone layer (stratosphere, 15–35 km altitude) absorbs harmful UV radiation from the Sun. CFCs (Chlorofluorocarbons) from refrigerants destroy the ozone layer, increasing UV reaching Earth → skin cancer risk.

Lamarck's theory of acquired characters was disproved because:

Acquired characters are not encoded in DNA and cannot be inherited

Darwin proved evolution happens by natural selection only

Acquired characters are not encoded in DNA and cannot be inherited

It was never tested in any experiment

Organisms don't adapt to environment

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Ecology, Microbes & Evolution

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Ecology, Microbes & Evolution — Complete Study Guide

Introduction to Ecology

Ecology is the branch of biology that studies the relationships between living organisms and their environment. The term "ecology" was coined by Ernst Haeckel in 1866, from the Greek words oikos (house) and logos (study). Ecology operates at multiple levels of organization: organisms, populations, communities, ecosystems, biomes, and the biosphere.

1. Levels of Ecological Organization

Level	Definition	Example
Individual	Single organism	One neem tree
Population	All individuals of one species in an area	All tigers in Ranthambore
Community	All populations in an area	All plants, animals, fungi in a forest
Ecosystem	Community + its abiotic environment	A pond, a forest, a coral reef
Biome	A large regional ecosystem with distinctive climate & organisms	Tropical rainforest, Desert, Tundra
Biosphere	All ecosystems on Earth	Life on the entire planet

2. Types of Ecosystems

A. Terrestrial Ecosystems:

Tropical Rainforest: High rainfall, maximum biodiversity, evergreen trees, found near equator (Amazon, Congo, Western Ghats)
Deciduous Forest: Moderate rainfall, trees shed leaves in dry season, most of India's forests
Grassland (Savanna): Grasses dominate, sparse trees, large herbivores — African savanna, Indian grasslands
Desert: Very low rainfall (<25 cm/year), extreme temperatures, xerophytes (cacti, camels, rats)
Tundra: Near poles, permanently frozen subsoil (permafrost), very few species, lichens & mosses

B. Aquatic Ecosystems:

Freshwater: Lakes, ponds, rivers, wetlands — less salinity
Marine: Ocean, coral reefs, deep sea — high salinity (35 ppt)
Estuarine: Where river meets sea — high productivity, nursery for many fish

3. Energy Flow in Ecosystems

Food Chain: A linear sequence showing who eats whom.

Example: Grass → Grasshopper → Frog → Snake → Eagle

Components:

Producers (Autotrophs): Organisms that make their own food via photosynthesis (plants, algae) or chemosynthesis (some bacteria). They form the base of all food chains.
Consumers (Heterotrophs): Animals that eat others.
- Primary Consumers (Herbivores): Eat plants (rabbit, deer, grasshopper)
- Secondary Consumers: Eat herbivores (frog, fox)
- Tertiary Consumers: Eat secondary consumers (eagle, lion)
Decomposers (Detritivores): Fungi and bacteria that break down dead organic matter, returning nutrients to the soil. They are essential recyclers.

Lindeman's 10% Rule (Law of Ecological Efficiency): Only 10% of the energy at one trophic level is transferred to the next. The remaining 90% is lost as heat during respiration, movement, and waste.

Example (with 1000 J at producer level):

Producers: 1000 J
Primary Consumer: 100 J
Secondary Consumer: 10 J
Tertiary Consumer: 1 J

Significance: This is why food chains rarely exceed 4–5 trophic levels. It also explains why eating lower on the food chain (plant-based diet) is more energy-efficient.

Food Web: Multiple interconnected food chains. More complex = more stable ecosystem.

Ecological Pyramids: Graphical representation of feeding relationships.

Pyramid of Numbers: Number of organisms at each level (inverted in parasitic chains)
Pyramid of Biomass: Total dry weight at each level (always upright in terrestrial)
Pyramid of Energy: Always upright — energy always decreases up the chain

4. Biogeochemical Cycles (Nutrient Cycling)

A. Nitrogen Cycle:

78% of atmosphere is N₂, but most organisms cannot use it directly
Nitrogen Fixation: Conversion of N₂ to ammonia (NH₃) — done by Rhizobium (in legume roots), Azospirillum, blue-green algae (Anabaena, Nostoc)
Nitrification: Conversion of NH₃ → Nitrites (NO₂⁻) → Nitrates (NO₃⁻) by Nitrosomonas and Nitrobacter bacteria
Denitrification: Conversion of nitrates back to N₂ by Pseudomonas bacteria — completes the cycle

B. Carbon Cycle:

Carbon moves via photosynthesis (CO₂ → organic), respiration (organic → CO₂), decomposition, and combustion
Rising CO₂ due to fossil fuels causes greenhouse warming

C. Water Cycle (Hydrological Cycle):

Evaporation → Condensation → Precipitation → Surface runoff/Groundwater → Evaporation
Transpiration by plants adds significant water vapor to atmosphere

5. Ecological Relationships (Biotic Interactions)

Relationship	Effect on species 1	Effect on species 2	Example
Mutualism	+	+	Bee & flower, Bacteria in gut
Commensalism	+	0	Orchid on tree (epiphyte)
Parasitism	+	-	Tapeworm in human intestine
Predation	+	-	Lion hunting deer
Competition	-	-	Two species fighting for same food
Amensalism	0	-	Penicillium kills bacteria

6. Microorganisms in Welfare of Mankind

Beneficial Bacteria:

Bacterium	Function
Lactobacillus	Converts milk to curd (lactic acid fermentation)
Rhizobium	Nitrogen fixation in root nodules of legumes
Bacillus thuringiensis (Bt)	Biological pesticide used in Bt Cotton, Bt Brinjal
Streptomyces	Produces Streptomycin antibiotic
Clostridium	Anaerobic nitrogen fixation in soil

Beneficial Fungi:

Fungus	Function
Saccharomyces cerevisiae (Yeast)	Fermentation for bread, beer, wine
Penicillium notatum	Produces Penicillin (first antibiotic — discovered by Alexander Fleming, 1928)
Aspergillus niger	Produces Citric acid (food industry)
Rhizopus	Used in steroid production

Microbes in Agriculture:

Biofertilizers: Rhizobium, Azospirillum, Blue-green algae (BGA)
Biopesticides: Bt toxin from Bacillus thuringiensis
Mycorrhizae: Helpful fungi that increase root absorption of water and minerals

Microbes in Industry:

Fermentation: Alcohol production (ethanol from glucose)
Cheese production: Specific bacteria cultures
Biogas (Methane): Produced by methanogenic archaea/bacteria from organic waste

7. Biodiversity

Definition: The variety of life on Earth at three levels:

Genetic Diversity: Variations within a species (e.g., different mango varieties)
Species Diversity: Variety of species in an area
Ecosystem Diversity: Variety of habitats/ecosystems

India's Biodiversity Status:

India is one of the 17 Megadiverse Countries in the world
Has 2–3% of world's land but contains ~7% of world's species
Biodiversity Hotspots in India: Western Ghats (with Sri Lanka), Eastern Himalayas (Indo-Burma), Sundaland (Andaman & Nicobar)

Threats to Biodiversity (Acronym: HIPPO):

H: Habitat destruction (deforestation, urbanization) — the #1 cause
I: Invasive alien species (e.g., water hyacinth, Lantana)
P: Pollution (air, water, soil)
P: Population pressure (overexploitation)
O: Overexploitation (overfishing, poaching)

Conservation Strategies:

In-situ Conservation: Protecting species in their natural habitat
- National Parks, Wildlife Sanctuaries, Biosphere Reserves
- Project Tiger: Started 1973 — most successful conservation project
- Project Elephant: Started 1992
Ex-situ Conservation: Protecting species outside their natural habitat
- Zoos, Botanical Gardens, Seed Banks
- National Bureau of Plant Genetic Resources (NBPGR): New Delhi

Red Data Book: Published by IUCN — lists all endangered, vulnerable, and threatened species globally.

Categories: Extinct → Extinct in Wild → Critically Endangered → Endangered → Vulnerable → Near Threatened → Least Concern

8. Theory of Evolution

A. Jean-Baptiste de Lamarck (1809):

Theory of Acquired Characters / Use and Disuse
Features acquired during lifetime can be inherited by offspring
Famous Example: Giraffes stretched necks by use → passed long necks to offspring
Status: DISPROVED — acquired characters are not inherited (not encoded in DNA)

B. Charles Darwin (1859) — On the Origin of Species:

Theory of Natural Selection: organisms with favorable variations survive and reproduce
Key observations:
1. Organisms produce more offspring than can survive
2. Natural variation exists within populations
3. Some variations are heritable
4. Organisms with advantageous traits survive and reproduce (Survival of the Fittest)
Evidence: Fossil record, comparative anatomy, biogeography, molecular evidence

C. Modern Synthetic Theory (Neo-Darwinism):

Combines Darwin's natural selection with Mendel's genetics and Weismann's population genetics
Mutations + Natural Selection + Genetic Drift → Evolution

Homologous Organs: Same structure, different function → common ancestor

Example: Forelimbs of human, bat, whale, horse — all have same bone arrangement (humerus, radius, ulna)

Analogous Organs: Different structure, same function → convergent evolution

Example: Wings of butterfly and bat

Vestigial Organs: Organs that are functionless remnants of formerly useful organs

In humans: Appendix, coccyx, ear muscles, body hair
In snakes: Vestigial hind limb bones

9. Pollution and its Effects

Air Pollution:

Acid Rain: Caused by SO₂ (from coal burning) and NOₓ (from vehicle exhaust). pH drops below 5.6. Damages stone monuments (Marble Cancer — Taj Mahal), forests, lakes.
Global Warming: CO₂, CH₄, N₂O, CFCs trap infrared radiation → Greenhouse Effect → temperature rise → climate change
Ozone Depletion: CFCs (Chlorofluorocarbons) from refrigerants destroy ozone layer → More UV radiation → Skin cancer, cataracts
Smog: Smoke + Fog. Photochemical smog contains ozone and PAN (Peroxyacetyl Nitrate) — harmful to lungs

Water Pollution:

Eutrophication: Excess nutrients (nitrates, phosphates) in water → algal bloom → oxygen depletion → death of aquatic life
BOD (Biological Oxygen Demand): Amount of oxygen required by microorganisms to decompose organic matter. High BOD = highly polluted water.

Keystone Species: Species with a disproportionately large effect on ecosystem relative to their abundance.

Example: Sea otter (controls sea urchin populations, protects kelp forests), Elephants, Wolves

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