Life continues yet constantly changes. This SL lesson covers D3.1 Reproduction, D3.2 Inheritance, D3.3 Homeostasis, D4.1 Natural selection, D4.2 Stability & change and D4.3 Climate change.
You will use Punnett squares, follow feedback control, and connect natural selection to climate change.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you are ready.
Asexual reproduction (one parent, mitosis) gives identical clones — fast, but low variation.
Sexual reproduction uses meiosis to make haploid gametes, which fuse at fertilisation. This creates genetic variation through independent assortment, crossing over and random fertilisation.
In humans the menstrual cycle is coordinated by hormones (FSH, LH, oestrogen, progesterone).
Mendel showed characteristics are inherited as discrete alleles. Terms: genotype (alleles present), phenotype (observed trait), homozygous (two same alleles), heterozygous (two different).
A Punnett square predicts offspring ratios. A cross of two heterozygotes (Aa × Aa) gives a 3:1 phenotype ratio and a 1:2:1 genotype ratio.
Homeostasis keeps the internal environment within narrow limits using negative feedback: a change is detected and reversed toward a set point.
Sort each example into the correct category.
Natural selection needs variation, a struggle for existence (overproduction), and differential survival and reproduction of the fittest variants. Over generations, advantageous alleles increase in frequency.
Antibiotic resistance is a clear example: resistant bacteria survive treatment and pass on the resistance allele.
Ecosystems can be stable yet change; keystone species have large effects, and crossing a tipping point can shift a system abruptly.
Climate change: rising greenhouse gases (mainly CO2 from burning fossil fuels) trap infrared radiation, warming the planet and shifting species distributions and timings.
Match each term to its correct description.
D3.1-D3.2: meiosis and fertilisation create variation; Punnett squares predict ratios
D3.3: homeostasis uses negative feedback (glucose, temperature, water)
D4.1: natural selection increases advantageous alleles (e.g. antibiotic resistance)
D4.2-D4.3: tipping points and keystone species; CO2 drives climate change
Press Finish to see your score.
You have worked through Theme D: Continuity & Change — Organisms & Ecosystems for IB Diploma Biology. 🎉
Your stars: 0 / 0
Next: test yourself in the Evaluate stage Confidence Quiz, then lock it in with Verify.