Unit notes and practice questions
Everything here is for unit 6 of the Grade 11 Biology textbook: what the chapter covers, the short notes, practice questions with their answers, and the lesson video where one exists.
The cards filed under this chapter on the Grade 11 Biology page. Open one at a time.
When you use it
Use to calculate population growth rate under resource limitation and carrying capacity constraints.
Watch out
When N equals K, the term (K - N)/K becomes zero, leveling off population growth completely.
Drafted from Grade 11 Biology, page 236 onwards, then checked twice before it went up
| Factor Type | Mechanism | Factor Nature | Examples |
|---|---|---|---|
| Density-dependent | Impact changes with population density | Biotic | Predation, competition, disease, waste |
| Density-independent | Impact is unaffected by population density | Abiotic | Weather, earthquakes, floods, pollution |
When you use it
Use to distinguish between biotic and abiotic regulators of population size.
Watch out
Density-independent events kill a similar proportion of organisms regardless of whether the population is dense or sparse.
Drafted from Grade 11 Biology, page 236 onwards, then checked twice before it went up
When you use it
Use when estimating the total population size of immobile or slow moving organisms in a defined area.
Watch out
Ensure a is the combined total area of all placed quadrats, not the area of a single quadrat.
Drafted from Grade 11 Biology, page 236 onwards, then checked twice before it went up
| Type | Offspring Count | Parental Care | Mortality Timing | Examples |
|---|---|---|---|---|
| Type I | Few | High | Mostly in older age | Humans, large mammals |
| Type II | Moderate | Moderate | Constant across all ages | Some birds |
| Type III | Many | Little or none | Highest in early life | Plants, fish, invertebrates |
When you use it
Use to classify organisms based on their survival patterns, offspring investment, and age-specific mortality.
Watch out
Type II curves exhibit a constant mortality rate over the entire life span, not variable mortality.
Drafted from Grade 11 Biology, page 236 onwards, then checked twice before it went up
10 multiple-choice questions written against this chapter, each with its answer and the reason. Try one before you open the answer.
Question 1
Which sampling method is most appropriate to estimate the population size of mobile animals such as birds or rats?
Answer: A Mark-recapture method
Why
The textbook states that the mark-recapture method is used for moving animals, whereas the quadrat method is used for immobile organisms such as plants.
Question 2
When individuals in a population are clustered together in groups across a habitat, which dispersal pattern is present?
Answer: A Clumped dispersion
Why
Clumped dispersion occurs when individuals of a population are clustered in groups.
Question 3
Which type of survivorship curve is typical of humans and most mammals, where mortality is low in early and middle years and highest in old age?
Answer: A Type I
Why
Type I survivorship curve describes organisms that produce few offspring, provide high parental care, and have mortality concentrated mostly in older individuals.
Question 4
Which of the following is classified as a non-renewable natural resource?
Answer: A Coal
Why
Coal, minerals, and fossil fuels are non-renewable resources because their rate of consumption exceeds their rate of natural recovery.
Question 5
What condition is described when the per capita rate of increase (r) equals zero?
Answer: A Zero population growth
Why
When r is zero, the population size is unchanging, which is defined as zero population growth.
Question 6
In which census method does the government fix a single date (often a full-moon night) to count everyone present in the country?
Answer: A De Facto method
Why
The De Facto method conducts the census on a single fixed date throughout the country, whereas the De Jure method covers an enumeration period of two or three weeks and counts permanent residents.
Question 7
What does an expansive population pyramid with a broad base and a narrow top indicate about a population?
Answer: A A large percentage of young people with high fertility rates
Why
Expansive pyramids have a broad base representing a large proportion of young individuals and reflect high fertility rates with lower life expectancies.
Question 8
Which of the following is a density-independent (abiotic) factor that regulates population growth?
Answer: A Catastrophic earthquake
Why
Natural disasters like earthquakes, weather, and pollution are density-independent abiotic factors because they affect organisms regardless of population density.
Question 9
A biology student in Awash marked and released 60 birds. In a second capture of 100 birds, 20 were marked and 80 were unmarked. What is the estimated total bird population size (N)?
Answer: A 300
Why
Using the mark-recapture formula N = (M * n) / X: N = (60 * 100) / 20 = 6000 / 20 = 300 birds.
Question 10
In the logistic growth formula dN/dt = rN(K - N)/K, what does K represent?
Answer: A Carrying capacity
Why
K represents the carrying capacity, which is the maximum population size that available environmental resources can support.
The app holds 12 questions on this unit, marked as you go. These are the first 10.
The whole Grade 11 Biology textbook, free as a PDF.
Ministry of Education edition, English, 294 pages
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