Ecology | CEE Academy

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ECOLOGY

▢ Terms and Scientists:

Table 1: Important Ecology Terms

Term / Concept	Given by / Father	Point
Ecology	Ernst Haeckel	Reciprocal relationship between living organisms and environment
Ecology	Reiter	First authentic use
Father of Ecology	Reiter	Important exam point
Ecosystem	Tansley	Term ecosystem
Father of Ecosystem	Odum	Important exam point

▢ Branches of Ecology:

Table 1: Branches

Branch	Study
Autecology	Individual species / population and its habitat
Synecology	Community

▢ Speciation:

Table 1: Allopatry vs Sympatry

Type	Isolation	Species	Location	Developed character
Allopatry	Geographical isolation	Individuals of same species	Different geographical locations with/without barrier	Different morphological characters
Sympatry	Reproductive isolation	Individuals of same species	Same geographical location	Different morphological characters

▢ Important Ecological Terms:

Table 1: Ecological Terms

Term	Meaning	Example / Point
Ecotone	Transition zone between two communities	Estuary = ecotone between freshwater and saline water
Ecesis	Establishment of plant in new area during secondary succession	Succession term
Ecotype	Genetically different species in similar environment develop similar characters	Genetic difference + similar environment
Ecads / Ecophene	Genetically similar individuals in different environments develop different characters	Environmental variation
Niche	Habit, function and occupation of organism	Term by Grinnell; high competition
Keystone species	Most influencing species determining ecosystem properties	Kangaroo in taiga; reptiles in desert
Noosphere	Sphere dominated by human mind	Greenhouse, culture media

▢ Ecological Laws:

Table 1: Ecological Laws

Law	Statement
Allen's law	Tail, snout, ears and legs of mammals in colder regions are shorter
Bergmann's law	Mammals of colder regions are larger
Jordan's law	Fishes of cold water have more vertebrae

▢ Ecological Factors:

❖ Definition: Factors determining distribution of organisms

❖ Light:

Table 1: Light-based Plant Types

Type	Meaning
Heliophytes	Sun-loving plants
Sciophytes	Shade-loving plants
Facultative heliophytes	Sciophytes that can grow in sunlight
Facultative sciophytes	Heliophytes that can also grow in shade

❖ Temperature:

Table 1: Temperature Tolerance

Type	Meaning
Eurythermal	Can tolerate wide range of temperature
Stenothermal	Can tolerate narrow range of temperature

Table 2: Temperature-based Vegetation

Type	Temperature	Examples
Megatherms	High temperature	Desert, tropical rainforest
Mesotherms	High summer + low winter temperature	Temperate vegetation, pond flora
Microtherms	Low temperature	Conifer vegetation
Hekistotherms	Extremely low temperature	Tundra vegetation

❖ Other Factors:

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Wind
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Humidity
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Rainfall

❖ Humidity: Relative humidity measured by psychrometer

▢ Xerophytes:

❖ Definition: Plants adapted to dry / water-deficient conditions

❖ Adaptations:

Table 1: Xerophytic Adaptations

Part	Adaptation
Root	Highly developed root system, abundant root hairs, well-developed vascular system
Leaf	Reduced leaves, sunken stomata, multilayered epidermis
Stem	Reduced as phylloclade/cladode; succulent; water-storing parenchyma developed

◉ Leaf Examples:

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Multilayered epidermis → Ficus
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Multilayered epidermis → Nerium

❖ Types Based on Water Availability and Soil:

Table 1: Types of Xerophytes

Type	Condition
Physical xerophytes	Dry soil
Physiological xerophytes	Saline soil or very low temperature

❖ Types Based on Life Cycle and Water Storage:

Table 1: Xerophyte Types

Type	Other name	Feature
Ephemerals	Drought escapers / drought evaders	Short-lived; complete life cycle during rain
Succulents	Fleshy xerophytes / drought avoiders / drought resistant	Store water in root, stem or leaf
Non-succulents	True xerophytes / drought tolerant	Withstand long drought periods

◉ Succulent Types:

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Root succulents
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Stem succulents
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Leaf succulents

▢ Phytes:

Table 1: Plant Types Based on Habitat

Type	Plants growing in
Psilophytes	Savannah grassland
Psammophytes	Sand / sandy soil
Eremophytes	Desert

▢ Biogeochemical Cycle:

❖ Nitrogen Cycle:

◉ Nitrogen Fixation:

Table 1: Types of Nitrogen Fixation

Type	Agent / Example	Point
Natural	Thunderstorm, lightning	Atmospheric fixation
Biological symbiotic	Rhizobium	Root nodules; nif gene; leg-haemoglobin; nitrogenase activity
Biological non-symbiotic	Clostridium, Rhodospirillum	Free nitrogen fixation
Free-living	Azotobacter	Free-living nitrogen fixer
Cyanobacteria / BGA	Anabaena, Nostoc	Heterocyst for nitrogen fixation
Fungi	Mycorrhiza	Basidiomycetes + roots
Artificial	Industrial process	Artificial fixation

◉ Mycorrhiza:

Table 1: Mycorrhiza Types

Type	Feature
Ectomycorrhiza	Less beneficial; fungal hyphae outside root cells
Endomycorrhiza	Mycelium inside cells; stores nitrogen compounds; forms VAM
VAM	Vesicular Arbuscular Mycorrhiza

◉ Steps:

Table 1: Nitrogen Cycle Processes

Process	Meaning / Reaction
Nitrogen fixation	Conversion of atmospheric nitrogen into usable compounds
Nitrification	Ammonia → nitrite → nitrate
Nitrogen assimilation	Utilization of nitrogenous compounds by organisms
Ammonification	Complex nitrogenous compounds → ammonium compounds by microbes after death
Denitrification	Soil nitrogen compounds → free atmospheric nitrogen
Sedimentation	Nitrogenous compounds enter soil particles

◉ Nitrification: \(NH_3 \xrightarrow{Nitrosomonas} NO_2^- \xrightarrow{Nitrobacter} NO_3^-\)

◉ Denitrifying Bacteria:

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Pseudomonas
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Nitrosomonas denitrificans

◉ Note: Nitrogen fixation and denitrification are anaerobic events

▢ Flow in Biology:

Table 1: Direction of Flow

Process	Direction
Energy flow	Unidirectional →
Energy pathway	Sunlight → different trophic levels in linear pathway
Ascent of sap	Unidirectional →
Translocation of food in phloem	Bidirectional ↔
Biogeochemical cycle	Bidirectional ↔
DNA replication	Bidirectional ↔

▢ Ecological Pyramids:

Table 1: Pyramids in Ecosystems

Ecosystem	Pyramid of Energy	Pyramid of Number	Pyramid of Biomass
Grassland ecosystem	Upright	Upright	Upright
Forest ecosystem	Upright	Upright	Upright
Pond / sea ecosystem	Upright	Upright	Inverted
Parasitic ecosystem	—	Inverted	—
Unstable ecosystem	Inverted	—	—
Tree ecosystem	Upright	Inverted	Upright

❖ Note: Pyramid of energy is always upright in stable natural ecosystems

▢ Ecological Study:

Table 1: Study Terms

Study	Term
Soil	Edaphology / Pedology

▢ Pioneer Organisms:

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Cyanobacteria
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Bacteria
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Lichen

▢ Soil Profile:

❖ Definition: Nature and sequence of different layers / horizons in vertical section of soil

Table 1: Soil Horizons

Horizon	Region	Content
A00 horizon	Litter region	Undecomposed organic matter
A0 horizon	Duff region	Partially decomposed organic matter
O horizon	Organic horizon	A00 + A0
A1 horizon	Humus layer	Fully decomposed organic matter
A2 horizon	Mineral + little humus	Mineral particles with little humus
A horizon	Top mineral horizon	A1 + A2
B horizon	Mineral horizon	Only mineral particles
Top soil	A00 + A0 + A1 + A2 + B	About 15–20 cm thick
C horizon	Weathered rock	Incompletely broken mineral particles
R horizon	Bed rock	Unbroken rocks
Sub-soil	C + R	Lower soil layers

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ECOLOGICAL IMBALANCE AND POLLUTION

▢ Air Pollution:

Table 1: Air Pollutants

Pollutant / Source	Important points
Automobile exhaust	Contains CO, NOx and unburnt hydrocarbons
Lead	Affects nervous system; soil pollutant
Fly ash	Fine ash particles in fuel gas; expelled from thermal power plants
Smoke	Contains 3,4-benzopyrene causing lung cancer
CO	Air pollutant
SO₂	Affects Taj Mahal; causes respiratory disorder; affects membrane systems
Acid rain	Mainly due to SO₂ pollution
Smog	Smoke + fog; common at low temperature
Photochemical smog	NOx + hydrocarbons + oxygen in bright sunlight → O₃ + PAN
PAN	Peroxyacetyl nitrate; causes eye irritation
Greenhouse effect	CO₂ major for Earth; CH₄ and CFCs highly effective
Methane	Produced by paddy fields; involved in global warming
Aerosol	Air pollutant
Ozone problem	Ozone layer depletion / ozone pollution
Plant-origin pollutants	Pollens and plant particles

❖ Air Pollution Control: Cyclone collector minimizes air pollution

▢ Water Pollution:

Table 1: Water Pollutants

Cause / Term	Point
Sewage	Causes ecosystem collapse due to lack of dissolved oxygen
Industrial wastes	Heavy metal poisoning
Cadmium poisoning	Itai-itai disease in Japan
Mercury poisoning	Minamata disease in Minamata city, Japan
Fertilizer pollution	Causes nutrient enrichment
Eutrophication	Nutrient enrichment of water body; reduces dissolved oxygen
Eutrophic lake	Shallow lake rich in organic products
Polluted lake index	Daphnia
BOD	Biochemical oxygen demand
Biomagnification	Pesticides/heavy metals become more concentrated at each food chain level

❖ BOD:

◉ Definition: Measure of oxygen needed in specified volume of water to decompose organic matter

◉ Importance: Measures polluting organic matter in water sample

▢ Other Pollution:

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Soil pollution
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Noise pollution
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Radioactive pollution

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WILDLIFE AND CONSERVATION

▢ Threatened Species:

Table 1: Threat Categories

Category	Meaning
Endangered	Number reduced to critical level; immediate danger of extinction
Vulnerable	Likely to become endangered if causal factors continue
Rare	Small populations; not presently endangered/vulnerable but at risk

▢ Wildlife Reserves of Nepal:

Table 1: Wildlife Reserves

Reserve	Important point
Parsa Wildlife Reserve	Wildlife reserve
Koshi Tappu Wildlife Reserve	Wildlife reserve
Shuklaphanta Wildlife Reserve	Wildlife reserve
Dhorpatan Hunting Reserve	Only hunting reserve of Nepal

▢ National Parks of Nepal:

Table 1: National Parks

National Park	Important point
Chitwan National Park	First national park of Nepal; World Heritage Site
Sagarmatha National Park	World Heritage Site
Shey Phoksundo National Park	Largest national park of Nepal
Khaptad National Park	National park
Langtang National Park	Famous for red panda
Bardia National Park	National park
Rara National Park	National park
Makalu Barun National Park and Conservation Area	National park and conservation area

▢ Endangered Wildlife of Nepal:

❖ Legal Protection: 27 mammals + 9 birds + 3 reptiles = 39 species protected under National Parks and Wildlife Act 1973

❖ Reptiles:

Table 1: Protected Reptiles

Common name	Scientific name
Gharial	—
Golden monitor lizard	—

❖ Birds:

Table 1: Protected Birds

Common name	Scientific name
Great hornbill	—
Impeyan pheasant	—
Bengal florican	—

❖ Mammals:

Table 1: Protected Mammals

Common name	Important point
Asiatic elephant	Protected mammal
One-horned rhinoceros	Protected mammal
Four-horned antelope	Protected mammal
Bengal tiger	Protected mammal
Snow leopard	Protected in alpine region
Red panda	Protected mammal
Himalayan musk deer	Protected mammal
Spotted deer	Protected mammal
Swamp deer	Protected mammal
Dolphin	Protected mammal
Black buck	Protected mammal

❖ Endangered Flora: —

▢ Conservation:

Table 1: In situ vs Ex situ Conservation

Type	Meaning	Examples / Techniques
In situ conservation	Conservation of ecosystems, natural habitats and viable populations in natural surroundings	National parks, wildlife reserves, protected areas
Ex situ conservation	Conservation of biodiversity outside natural habitat	Zoo, captive breeding, aquarium, botanical garden, gene bank

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HIGH-YIELD RECALL

Table 1: Ecology One-Liners

Fact	Answer
Term ecology given by	Ernst Haeckel
First authentic use of ecology	Reiter
Father of ecology	Reiter
Term ecosystem	Tansley
Father of ecosystem	Odum
Autecology	Individual species / population
Synecology	Community
Geographical isolation	Allopatry
Reproductive isolation	Sympatry
Transition zone	Ecotone
Freshwater + saline water ecotone	Estuary
Establishment in new area	Ecesis
Term niche	Grinnell
Most influencing species	Keystone species
Sphere dominated by human mind	Noosphere
Short extremities in cold mammals	Allen's law
Large mammals in cold regions	Bergmann's law
Cold-water fishes have more vertebrae	Jordan's law
Sun-loving plants	Heliophytes
Shade-loving plants	Sciophytes
Wide temperature tolerance	Eurythermal
Narrow temperature tolerance	Stenothermal
Relative humidity measured by	Psychrometer
Dry-soil xerophytes	Physical xerophytes
Saline/cold-soil xerophytes	Physiological xerophytes
Drought escapers	Ephemerals
True xerophytes	Non-succulents
Plants of sandy soil	Psammophytes
Plants of desert	Eremophytes
Symbiotic nitrogen fixer	Rhizobium
Free-living nitrogen fixer	Azotobacter
Cyanobacterial nitrogen fixers	Anabaena, Nostoc
Special N₂-fixing cell	Heterocyst
Anaerobic events in nitrogen cycle	Nitrogen fixation and denitrification
Energy flow	Unidirectional
Food translocation in phloem	Bidirectional
Pond biomass pyramid	Inverted
Tree ecosystem number pyramid	Inverted
Study of soil	Edaphology / Pedology
Pioneer organisms	Cyanobacteria, bacteria, lichen
Undecomposed organic layer	A00 / litter
Partially decomposed layer	A0 / duff
Humus layer	A1 horizon
Fly ash source	Thermal power plants
Lead affects	Nervous system
Lung cancer pollutant	3,4-benzopyrene
Taj Mahal affected by	SO₂
Acid rain mainly due to	SO₂
Smog	Smoke + fog
PAN causes	Eye irritation
Major greenhouse gas for Earth	CO₂
Paddy field gas	Methane
Cadmium poisoning	Itai-itai disease
Mercury poisoning	Minamata disease
Index of polluted lake	Daphnia
BOD	Organic pollution index of water
Biomagnification	Increase of toxic concentration at successive trophic levels
Air pollution control device	Cyclone collector
Only hunting reserve of Nepal	Dhorpatan Hunting Reserve
First national park of Nepal	Chitwan National Park
Largest national park of Nepal	Shey Phoksundo National Park
National park famous for red panda	Langtang National Park
In situ conservation	In natural habitat
Ex situ conservation	Outside natural habitat

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