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1.Research (15–20 min)
Use your textbook, class notes, and other reliable sources to investigate your assigned concept.

🟢 Molecular Evidence
🟠 Fossil Record
🔵 Selective Breeding
🟣 Homologous Structures
🔴 Analogous Structures

2. Create a Visual Display (on Padlet):
include the following:

✅ a clear definition or explanation of the concept.

✅ a real-world example (e.g. dna sequences in humans vs chimps, dog breeding, pentadactyl limb, analogous wings).

✅ a diagram or labeled image to illustrate the idea.

✅ a short quiz question or challenge to test your classmates.

3. Share (10–15 min)

present your branch to the class.

add your work to the class evolution tree, showing how each concept is a piece of the larger picture of evolution.

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Analogous structures are unrelated body parts or organs that perform a similar function, such as the wings of a bird and an insect, and are the result of convergent evolution—the independent evolution of similar features in different species due to similar environmental pressures or lifestyles.

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A Real life example of selective breeding

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A Real life example of selective breeding

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Dog breeding : derived from domestication of wolves around 30,000 - 40,000 years ago. Different breeds are developed for various purposes; ie for herding (Border Collies), for hunting (greyhounds) and for companionship (chihuahuas)

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The fins, wings, and flippers of sharks, penguins, and dolphin. Though the structures are different, the function is the same: they aid in swimming. These examples show how unrelated organisms independently evolve similar traits to adapt to similar environments and ecological roles

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Homologous structures are similar anatomical features found in different species that have a common underlying structure and origin from a common ancestor. While the basic structure is conserved, these organs or parts have been modified over time through divergent evolution to perform different functions, serving as strong evidence for evolution.

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Definition: Also known as molecular phylogeny, molecular evidence of evolution is the comparative analysis of the nucleotide sequences of DNA and RNA and the amino acid sequences of proteins between organisms.

Real World Example: Chimpanzees and humans turn out to be very similar if you look at their DNA. When scientists determined the entire genetic code of both humans and chimpanzees, they found that we have over 98% identical DNA. The 2nd Chromosome in the human genome is similar to two chimpanzee chromosomes which have been "split apart" showing molecular similarity between the two species and evidence of evolution.

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A common real-world example of homologous structures is the forelimbs of various vertebrates, such as humans, bats, whales, and cheetahs. These limbs share a similar underlying bone structure: including the humerus, radius, and ulna which are inherited from a common ancestor, but they have been modified over time to perform different functions, like walking, flying, or swimming.

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Fossil records are the collection of preserved remains, impressions, or traces of organisms from past geological ages found in sedimentary rock layers. It provides a chronological evidence of the history of species, showing when different organisms existed, how they changed over time, and how major groups are related. Fossils are dated using relative methods (stratigraphy) and absolute methods (radiometric dating).

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Labelled diagram of selective breeding process 

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Labelled diagram of selective breeding process 

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Q1. Which of the following best describes homologous structures?

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A. Body parts that have the same function but evolved independently in different species.

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B. Body parts that are similar in structure due to common ancestry but may serve different functions.

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C. Body parts that are identical in structure and function across all species.

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D. Body parts that developed in unrelated species due to similar environmental pressures.

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1. State what is meant by homologous structures.

2.  Describe one example of a homologous structure in vertebrates.

3. Explain how homologous structures provide evidence for evolution.

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Q2. Which of the following is an example of homologous structures?

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A. Wings of a butterfly and wings of a batD. Eyes of an octopus and eyes of a human

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B. Flippers of a dolphin and arms of a human

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C. Tail fin of a fish and tail fin of a whale

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D. Eyes of an octopus and eyes of a human

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1) Which of the following best describes an analogous structure?

A. A structure in two different species that serves a similar function and was inherited from a common ancestor.

B. A structure in two different species that serves a similar function but evolved independently, without a common ancestor.

C. A structure found in all members of a species that performs the same function.

D. A structure found in all members of a species but serves different functions.

2) Looking at the picture above, which of the following would be considered analogous?

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Tiktaalik (∼375 million years ago): A fish–tetrapod transitional fossil with fins that have wrist-like bones — evidence for the evolution of limbs used in land locomotion.

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Selective breeding
Definition:domestication of plants and animals
→human control reproduction so that the control traits will be appear in the offspring
→therefore more desirable traits become more common
→humans continually select organisms with desirable characteristics, removing those with less
desirable traits, leading to a rapid genetic change in the population.
Used in agriculture to produce more crops and dairy products.
Artificial selection is the same as selective breeding.

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1. What does selective breeding demonstrate in terms of evolutionary changes?
A. It shows that evolution can only occur in wild species.
B. It provides evidence for rapid evolutionary changes in domesticated species.
C. It proves that all species evolve at the same rate.
D. It indicates that selective pressures have no impact on evolution.

2. Which of the following is an example of selective breeding?
A. Keeping animals in zoos
B. Breeding of wild mustard to create different
types of vegetable
C. Evolution of antibiotic resistance in bacteria
D. The pentadactyl limb of vertebrates

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1. State two ways that artificial selection / selective
breeding provides evidence for evolution?

2. Describe the process of selective breeding in plants.

3. Explain the advantages and disadvantages of selective breeding in animals.

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MCQs

1. B

2. B

1. Homologous structures are anatomical features that share a similar basic structure due to common ancestry, even if they serve different functions in different species.

2. The pentadactyl limb in vertebrates (e.g., human hand, bat wing, whale flipper) is homologous. While the bones differ in size and shape to perform functions such as grasping, flying, or swimming, the basic bone arrangement (humerus, radius, ulna, carpals, metacarpals, phalanges) is the same, showing common ancestry.

3.  Homologous structures demonstrate that different species share a common ancestor. The similarity in underlying bone structure, despite differences in function, suggests that species have diverged through adaptive radiation and natural selection, modifying the same basic design to suit different environments.

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Explain how molecular evidence can be used to understand the process of speciation.

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A fossil is the preserved remains or traces of any organism from the remote past. Preserved remains (body fossils) provide direct evidence of ancestral forms and include bones, teeth, shells, leaves, etc. The totality of fossils, both discovered and undiscovered, is referred to as the fossil record. (https://old-ib.bioninja.com.au/standard-level/topic-5-evolution-and-biodi/51-evidence-for-evolution/fossil-record.html)

A classic example of the fossil record demonstrating both evolution and speciation is the evolution of the horse, tracing from the small, dog-sized Hyracotherium with multiple toes to the large, single-toed modern horse, showing gradual changes in size, limb structure, and teeth suitable for different diets over millions of years

Questions:

What does the fossil record primarily provide evidence for?

A. The constant rate of mutation in DNA
B. The theory of acquired characteristics
C. The evolution of life over time
D. The spontaneous generation of species

Which of the following best explains why there are gaps in the fossil record?

A. All organisms fossilize easily
B. Evolution has stopped
C. Conditions for fossilization are rare
D. All transitional species have already been found

Outline how fossil records can provide evidence for evolution? (4 marks)

Discuss the strengths and limitations of using the fossil record as evidence for evolution.

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State which technique can be used to compare amino acid sequences between organisms/species

Describe the similarities between the DNA of various species

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1. B.

2. B

3. It shows that the heritable traits of a species can change over time
It shows that evolution can happen rapidly

4. Identify and select plants with desirable traits (e.g., high yield, disease resistance, larger fruit).
Cross-pollinate these parent plants.
Grow seeds from the cross and observe offspring.
Repeat selection and breeding over many generations until trait is established.

5. Advantages:
Improves desirable traits (e.g., more milk, meat, eggs, speed, temperament).
Increases efficiency in farming/food production.
Can create animals adapted to specific human needs.
Disadvantages:
Reduces genetic variation (risk of inbreeding).
Increases risk of genetic diseases or harmful traits (e.g., hip dysplasia in dogs).
Animals may suffer welfare issues (e.g., health problems from exaggerated traits).
Reduced adaptability to environmental change/disease.

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-El Chocon, Patagonia Argentina. by Azul

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3) Explain the theory of convergent evolution using named analogous structures as an example.

4) Describe how different species develop analogous structures.

5) State 2 ways in which convergent evolution differs from divergent evolution.

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Topic A 4.2 EDGE of Existence – Species Prioritization 

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Topic A 4.2 EDGE of Existence – Species Prioritization 

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Objective: Apply understanding of biodiversity loss, conservation approaches, and species prioritization.

Instructions:

1. Work in your group

2. You have been provided with a set of 6–8 fictional species profiles including:

Evolutionary distinctiveness

Global endangerment status

Habitat type

Threats faced

3. Each group must:

Rank the species in order of conservation priority using EDGE criteria.

Suggest conservation strategies (in situ, ex situ, community engagement, policy measures) for the top 2–3 species.

4. Groups present their rankings and justify their choices to the class.

5. Debrief: Discuss how real-world conservation programs, like EDGE, balance evolutionary importance, extinction risk, and practical feasibility.

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Group 1 Conservation approach [ Yakuba, Gabriella, Aaryn]

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Group 1 Conservation approach [ Yakuba, Gabriella, Aaryn]

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Group 2 Conservation approach [ Gargee, Devika, Rena]

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Group 2 Conservation approach [ Gargee, Devika, Rena]

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Group 3 Conservation approach [ Hanna, Anisa, Aashna, Fadilah]

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Group 3 Conservation approach [ Hanna, Anisa, Aashna, Fadilah]

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Group 4 Conservation approach [Joyce, Clara, Nampheng]

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Group 4 Conservation approach [Joyce, Clara, Nampheng]

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Group 5 Conservation approach [ Sivani, Palden, Bianca]

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Group 5 Conservation approach [ Sivani, Palden, Bianca]

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Group 6 Conservation approach [ Kanav, Rajveer, Vaishnavi]

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Group 6 Conservation approach [ Kanav, Rajveer, Vaishnavi]

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Ranking in order of conservation priority using EDGE

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Ranking in order of conservation priority using EDGE

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1. Glass-spined fish-40

2. Silvercrest Lizard-36

3. Bluefin Dartfrog-21 , Silverleaf-orchid-21

5. Crimson tailed tamarin-18

6. Golden-winged bat-16

7. Cloudback lemur-10

8. Emerald tree snake-4

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Silvercrest Lizard and Crimson-tailed Tamarin

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Silvercrest Lizard and Crimson-tailed Tamarin

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Silvercrest Lizard is 2nd on the EDGE score. Conservation strategies include:

mandate licenses for fishing, create natural reserves (in-situ), and breeding programs in aquariums (ex-situ).

Crimson-tailed Tamarin is 5th on the EDGE score. Conservation strategies include:

creating natural reserves so no new cities can be built (ex-situ), plant native species (in-situ), make policies to create wildlife corridors.

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Species Name and ranking based on EDGE Score (ED × GE)

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Species Name and ranking based on EDGE Score (ED × GE)

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1. Glass-spined Fish- 40

2. Silvercrest Lizard-36

3. Bluefin Dartfrog-21

4. Silverleaf Orchid-21

5. Crimson-tailed Tamarin-18

6.Golden-winged Bat-16

7. Cloudback Lemur-10

8. Emerald Tree Snake -4

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1. Glass-spined fish (40)

2. silvercrest lizard (36)

3. bluefin dartfrog (21)

4. silverleaf orchid (21)

5. crimson tailed tamarin (18)

6. golden-winged bat (16)

7. cloudback lemur (10)

8. emerald tree snake (4)

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1. Yes our group's ranking matched matched the EDGE scores because they were arranged in descending order of the calculated score. We considered the ED and GE.

2. Done in another post published above

3. The more evolutionary distinct and and endangered a species is the more pressure and need there is to take action as losing this species will affect the biodiversity.

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Ranking and EDGE score

1- 40- Glass-spined Fish

2- 36- Silvercrest Lizard

3.5 (tie)-21- Bluefin Dartfrog

3.5(tie)- 21- Silverleaf Orchid

5- 18-Crimson-tailed Tamarin

6-16- Golden-winged Bat

7-10-Cloudback Lemur

8-4-Emerald Tree Snake

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Glass spined fish:

Ex-situ conservation

Immediate action needs to be taken as the GE score is very high

Storing in zoos, aquariums as it is easy to simulate the conditions for its survival

Golden Winged Bat

In-situ conservation

Lower GE score, not as much of a risk

Policies banning hunting in temperate forests can help ensure the survival of these bats

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1. Glass spined fish (40)

2. Silvercrest lizard (36)

3. Bluefin Dart frog and Silverleaf Orchid (21)

4. -

5. Crimson tailed Tamarin (18)

6. Golden-winged Bat (16)

7. Cloudback lemur (10)

8. Emerald Tree Snake (4)

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1) Glass-Spined Fish: 40 (10 x 4)

2) Silvercrest Lizard: 36 (9 x 4)

3) Bluefin Dartfrog: 21 (7 x 3)

4) Crimson-Tailed: 18 (6 x 3)

5) Silverleaf Orchid: 21 (7 x 3)

6) Golden-Winged Bat: 16 (8 x 2)

7) Cloudback Lemur: 10 (5 x 2)

8) Emerald Tree Snake: 4 (4 x 1)

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How do evolutionary distinctiveness and endangerment status affect conservation decisions?

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How do evolutionary distinctiveness and endangerment status affect conservation decisions?

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Animals with a higher evolutionary distinctiveness and a higher endangerment status contribute to a higher global endangerment score and hence are prioritised more in the EDGE criteria. These animals are the ones that need urgent conservation efforts, not just in terms of in-situ or ex situ conservation but also by changing global policies, and increasing community engagement.

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Glass-spined Fish

Making new policies to stop fishing in areas where coral reefs are depleting

Coral gardening

Community engagement

Prevent overfishing of herbivorous fish that control algae

Establish Marine Protected Areas (MPAs)

Selective breeding and assisted evolution

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Silvercrest Lizard and Silverleaf Orchid

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Silvercrest Lizard and Silverleaf Orchid

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Silvercrest Lizard is 2nd on the EDGE score. Conservation strategies include:

mandate licenses for fishing, create natural reserves (in-situ), and breeding programs in aquariums (ex-situ).

Silverleaf Orchid is 3rd on the EDGE score. Conservation strategies include:

implementing policies so no new cities can be built, creating natural reserves, plant native species (in-situ), implementing fines for poaching, move to botanical gardens if habitat is too destroyed.

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Monitoring the spread of invasive species

ex-situ conservation as pollution is there and there’s only an extent to which we can monitor pollution

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1. Yes because the evolutionary distinctiveness for glass-spined fish is the highest and it is critically endangered.

2. Glass-spined fish --> develop laws related to fishing (fish by quota), create natural reserves with healthy corals (in-situ) Silvercrest Lizard --> Since they suffer from habitat loss, in-situ conservation strategies should be used. For example : creating reserves and having captive breeding (ex-situ)

3. The more endangered the species and the higher the evolutionary distinctiveness is, the higher the need is to take action related to conservation decisions.

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1) Glass-Spined Fish:

Protection of Coral Reef Areas

Ex-situ Conservation

Regulation of Overfishing

2) Cloudback Lemur:

Protection of montane forest regions

In-situ Conservation

Anti-poaching measures

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Conservation of Silvercrest Lizard (Desert Ecosystems)

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Conservation of Silvercrest Lizard (Desert Ecosystems)

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1. In-situ conservation

Habitat Protection:
Designate desert reserves where mining, off-road vehicles, and land conversion are restricted.

Climate Action:
Reforestation of desert margins and creation of “shade corridors” help reduce local temperature extremes.

Invasive Species Control:
Remove or manage introduced predators (like cats and dogs) that prey on the lizards.

Microhabitat Restoration:
Replant native shrubs and restore sand dune structure, which are vital for shelter and thermoregulation.

2. Ex-situ conservation

Captive Breeding Programs:
Breeding individuals in controlled environments (zoos or research facilities) to later release into protected desert zones.

Genetic Research:
Studying genetic diversity helps ensure reintroduced populations are resilient and not inbred.

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Conservation of Glass-spined Fish (Coral Reefs)

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Conservation of Glass-spined Fish (Coral Reefs)

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1. In-situ (within natural habitat) conservation

Marine Protected Areas (MPAs):
Establish “no-take zones” where fishing and coral extraction are banned, allowing reefs and fish populations to recover naturally.

Coral Reef Restoration:
Artificial reefs and coral nurseries (using coral fragments grown on underwater frames) help rebuild bleached or damaged reefs that the fish depend on.

Sustainable Fishing Regulations:
Introduce quotas and seasonal bans to reduce overfishing and bycatch that threaten reef species.

Pollution Control:
Reduce agricultural runoff and coastal sewage discharge to prevent algal blooms that suffocate coral ecosystems.

Climate Adaptation Programs:
Monitor sea temperature and coral bleaching events; develop “climate-resilient reefs” using heat-tolerant coral species.

2. Ex-situ (outside natural habitat) conservation

Captive Breeding in Aquariums:
Controlled breeding programs in large public aquariums maintain genetic diversity and can reintroduce individuals into restored reef sites.

Cryopreservation:
Storing gametes (sperm/eggs) in biobanks ensures the species’ genes are protected even if wild populations crash.

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1) C

2) C

3) Outline how fossil records can provide evidence for evolution? (4 marks)

(i) Fossil records show organisms from the past that are different from those present today, demonstrating that changes have occurred in species over time.

(ii) Fossils appear in a chronological order within rock strata, with simpler organisms found in older layers and more complex or modern organisms in newer layers, matching evolutionary expectations

(iii) By comparing fossils with living organisms, scientists observe gradual changes in morphology, showing transitional forms that link ancestral species to their descendants.

(iv) Fossils of extinct species show that many organisms that once existed no longer do, supporting the idea that new species arise from old ones through evolutionary change.

4) Discuss the strengths and limitations of using fossil record as evidence for evolution.

Strengths:

(i) Fossil records show chronological changes in organisms over time, revealing evolutionary trends such as increasing complexity or the appearance of new traits.

(ii) Transitional fossils provide clear links between major groups, such as between reptiles and birds, helping to trace the evolutionary pathway

(iii) Fossils document extinct species, demonstrating that some organisms have disappeared while others have originated, which supports the idea of descent with modification.

Disadvantage

(i) The fossil record is incomplete because not all organisms fossilize; soft-bodied species and those in certain environments may never leave fossils.

(ii) Fossilization is a rare event, so many intermediate forms are missing, making some evolutionary transitions difficult to reconstruct conclusively

(iii) Dating fossils and interpreting relationships can sometimes be imprecise or reliant on indirect evidence, leading to possible errors or controversies in evolutionary sequences.

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How do evolutionary distinctiveness and endangerment status affect conservation decisions?

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How do evolutionary distinctiveness and endangerment status affect conservation decisions?

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Evolutionary distinctiveness determines how unique a species is, while endangerment status determines how urgent its conservation is. Together, they help scientists and policymakers allocate limited resources effectively and protect both evolutionary heritage and species survival.