Organisms and Populations for NEET UG
Ecology starts with how single organisms cope with their surroundings and how populations grow. It ends with how species interact: competing, eating, helping or parasitising each other.
BiologyClass 1274 MCQs2 lessons13 flashcards2 memory tricks
Practise Organisms and Populations free
What you'll learn
- Population growth
Use the exponential and logistic growth models and population attributes. - Population interactions
Classify interactions between species by who benefits and who is harmed.
Key formulas
| Change in population density | Nₜ₊₁ = Nₜ + [(B + I) − (D + E)] |
|---|---|
| Exponential growth | dN/dt = rN |
| Logistic growth | dN/dt = rN (K − N)/K |
Memory tricks
(+, 0): orchid on a mango branch, barnacles on a whale, cattle egrets with grazing cattle. Mutualism (+, +), competition (−, −), predation and parasitism (+, −), amensalism (−, 0).
Exponential growth (dN/dt = rN) makes a J-curve. Logistic growth (dN/dt = rN(1 − N/K)) makes an S-curve that levels off at the carrying capacity K.
Try 3 NEET-style questions
Q1. The human liver fluke, a trematode parasite, completes its life cycle using
- only one host, the human
- a mosquito as an intermediate host
- a dog and a cat
- two intermediate hosts, a snail and a fish
Show answer
Answer: (4) two intermediate hosts, a snail and a fish
Many parasites have complex life cycles. The human liver fluke depends on two intermediate hosts, a snail and a fish, to complete its life cycle.
Q2. When the starfish Pisaster, an important predator, was removed from an enclosed intertidal area in Paine's experiment,
- more than 10 species of invertebrates became extinct within a year because of interspecific competition
- the number of invertebrate species increased greatly
- nothing changed
- the starfish population grew
Show answer
Answer: (1) more than 10 species of invertebrates became extinct within a year because of interspecific competition
Without Pisaster, more than 10 invertebrate species became extinct within a year due to increased interspecific competition. Predators help maintain species diversity by reducing competition among prey.
Q3. The number of births per 1000 individuals of a population per year is the
- death rate
- birth rate (natality)
- growth rate only
- carrying capacity
Show answer
Answer: (2) birth rate (natality)
Natality is the number of births during a period added to the population.
Practise all 74 questions Free · explanations for every option · see where you go wrong