Principles of Ecology

Ecology isn’t static — ecosystems evolve and change continuously.
Certain scientific principles govern this evolution — how life adapts, varies, evolves, and sometimes goes extinct.
Let’s explore these one by one.

🦎 Adaptation

— “The Art of Survival”

In nature, every organism faces challenges — heat, cold, salinity, lack of water, predators, etc.
To survive, it develops certain features or behaviors that help it live comfortably in its environment.

That’s called Adaptation — any structural, physiological, or behavioral change that helps an organism survive better.

Types of Adaptations:

(a) Morphological Adaptation

→ Change in body structure or external appearance.

Examples:

• In deserts, plants have:
  • Thick cuticles → reduce water loss.
  • Sunken stomata → minimize transpiration.
  • No leaves (as in Opuntia cactus); instead, leaves become spines and stem becomes green and flat to do photosynthesis.
• Mammals in cold regions have shorter ears and limbs → minimize heat loss (Allen’s Rule).
  Conversely, elephants have large ears to lose heat, since they can’t sweat.
• Hyperthermophiles (like Archaebacteria) thrive in 60°C+ — in hot springs or deep-sea vents.

👉 Nature designs the body according to the environment — not the other way around!

(b) Physiological Adaptation

→ Change in internal functioning of the body.

Example:

• In the deserts of North America, Kangaroo rats survive without drinking water.
  • They produce metabolic water (from fat oxidation).
  • They concentrate urine so that very little water is wasted.
• When humans go to high altitudes, we start breathing faster due to low oxygen.
  Over time, our body acclimatises — produces more RBCs, adjusts hemoglobin, and increases breathing rate.
  This short-term physiological adjustment is called Acclimatisation.

(c) Behavioural Adaptation

→ Change in habits or actions to deal with the environment.

Example:

• Desert lizards cannot control body temperature internally like mammals.
  They bask in sunlight to warm up and hide in shade to cool down.
• Some animals migrate or burrow underground during extreme heat or cold.

🪴 Special Case — Halophytes

Now, some plants grow where others can’t — in salty coastal areas or mangroves.
Such plants are called Halophytes — they show extraordinary adaptations to survive high salinity.

⚙️ Adaptations in Halophytes (Example: Rhizophora, Avicennia)

1. Special Root Systems:
   • Prop roots → come down from branches (for support & respiration).
   • Stilt roots → arise from stem base near soil.
   • Pneumatophores (air roots) → grow upward from mud for breathing.
2. Vivipary (unique reproduction):
   • Seeds germinate on the parent tree itself before falling, avoiding saline soil.
3. Salt Management:
   • Cellular sequestration: Salts stored in vacuoles or cell walls.
   • Tissue partitioning: Salts concentrated in older leaves which later drop.
   • Root exclusion: Roots prevent salt entry.
   • Salt excretion: Glands on leaves remove salt actively.
4. Altered Flowering:
   • Flowering during rainy season to reduce salt stress.

👉 These are the “superheroes” of the plant world 😊— they turn adversity into strength!

🧬 Variation — The Basis of Evolution

No two individuals, even within a species, are exactly the same.
These differences — in color, height, resistance, or traits — are called Variations.

Sources of Variation:

• Genetic changes — addition/deletion of genes.
• Mutations — random changes in DNA.
• Environmental factors — climate, geography, etc.

👉 Example: Differences in skin color, hair type, or blood group among humans — all show variation within species.

Why is variation important?
Because it gives options for survival — if the environment changes, some variants might adapt better.

Adaptive Radiation

— “One Ancestor, Many Forms”

Imagine one ancestral species entering a new environment with many “empty niches” (unoccupied roles).
Different groups adapt to fill different roles → leading to diversification.

That’s Adaptive Radiation — when one ancestral species evolves into many new species to exploit new habitats or resources.

Example:
Darwin’s finches on Galápagos Islands — all descended from one ancestor but developed different beak shapes based on their feeding habits (seeds, insects, flowers, etc.).

👉 It’s evolution “branching out” to fill new opportunities.

🐅 Speciation — Formation of New Species

Speciation = the process by which new species evolve from existing ones.
It’s driven by evolutionary forces like mutation, natural selection, and isolation.

Let’s understand the types 👇

Allopatric Speciation (Geographic Speciation)

• Populations of a species become geographically isolated (mountains, rivers, oceans).
• Over time, due to genetic drift and different environmental pressures, they evolve separately.
• Even if the barrier is later removed, they can no longer interbreed.

Example:
Masai giraffes are separated by the Gregory Rift (Tanzania–Kenya) — they’ve remained isolated and genetically distinct for 1000+ years.

Peripatric Speciation

• Peripatric speciation occurs when a small population becomes isolated at the edge (or periphery) of a larger population’s geographic range.
• Mechanism:  small peripheral population becomes isolated from the main group and, due to genetic drift and strong natural selection in its new environment, rapidly evolves into a new species.

Parapatric Speciation

• Populations are partially separated — limited gene flow.
• Over time, genetic differences accumulate → forming distinct species.
• Example: populations living along a mountain slope where altitude gradually changes.

Sympatric Speciation

• Occurs without physical barriers — within the same area.
• Happens due to disruptive selection — different groups specialize in different ecological niches, food, or mating preferences.
• Gradually, reproductive isolation develops → new species form.

Example:
Insects feeding on different host plants in the same area may evolve into separate species.

Hybridization

• When two different species mate, they produce hybrids.
  Example: Horse × Donkey = Mule.
• Sometimes, hybrids themselves become a new species (if they can reproduce and adapt).

In Summary

Type	Isolation Type	Population Size	Example	Key Process
Allopatric	Large-scale geographical barrier	Large	Masai giraffes separated by Rift Valley	Geographic isolation
Peripatric	Small peripheral population at edge	Small	Island finches, subway mosquitoes	Founder effect + drift
Parapatric	Partial isolation across gradient	Moderate	Mountain slope populations	Limited gene flow
Sympatric	No physical isolation	Large, same area	Insects feeding on different host plants	Niche specialization
Hybridization	Cross between two species	—	Horse × Donkey → Mule	Hybrid speciation

🧬 Mutation and Recombination

Mutation:
A change in the DNA sequence — like a spelling error in the genetic code.
It introduces new traits that may be beneficial or harmful.

Recombination:
During meiosis and fertilisation, genes get reshuffled → producing new combinations every generation.
This is why even siblings aren’t identical.

Together, mutation + recombination = genetic diversity, the raw material for natural selection to act upon.

🌿 Natural Selection

— “Nature’s Quality Control”

This is the central pillar of Darwin’s Theory of Evolution.

Charles Darwin and Alfred Wallace proposed that:

Nature “selects” the individuals best suited to the environment.

Let’s simplify 👇

• Every population has variations.
• Some variations help survival better (e.g., camouflage, drought resistance).
• These individuals survive longer, reproduce more, and pass on their beneficial genes.
• Over generations, such traits become common in the population.

This is Natural Selection — nature choosing the “fittest.”

👉 So, evolution is not about “strongest survives,” but “most adaptable survives.”

🧠 Evolution

— The Grand Process

Evolution is the long-term change in organisms over generations, driven by:

• Variation
• Adaptation
• Natural selection
• Speciation

Darwin and Wallace proposed this in 1859 (“Theory of Natural Selection”).
Later, genetics refined it — forming the Neo-Darwinism theory, combining Darwin’s ideas + Mendel’s genetics.

☠️ Extinction

— The Other Side of Evolution

If evolution is about emergence of species, extinction is about their disappearance.

Why does extinction happen?

• Environmental changes (climate shift, volcanic eruptions, etc.)
• Competition with other species
• Failure to adapt quickly

When a species can’t cope with changing conditions — it disappears forever.

🔺 Today, we are living through the 6th Mass Extinction — the Anthropogenic Extinction.
It’s human-induced — driven by deforestation, pollution, overexploitation, and climate change.

🌎 Summary Table

Concept	Meaning	Example
Adaptation	Traits helping survival	Kangaroo rat, cactus
Variation	Differences within species	Skin color, blood type
Adaptive Radiation	One ancestor → many forms	Darwin’s finches
Speciation	Formation of new species	Masai giraffes (Allopatric)
Mutation	DNA change creating new genes	Sickle-cell mutation
Natural Selection	Nature favors best-suited traits	Camouflaged moths in industry
Evolution	Gradual change → new species	From reptiles → birds
Extinction	Permanent loss of species	Dodo, Woolly mammoth