Worksheet

Red Koi and Glowing Larvae: A Pond Study Day

Grade 8 practice: read histograms from a koi club's breeding round and a mosquito lab's cage test to explain how selection and engineering change traits.

Grade 8ScienceInteractive · Printable

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1 NGSS standard
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12 questions
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Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Circle the answer, Sorting, Short answer

About this worksheet

What students practice

Students use histogram data to explain how artificial selection shifted a trait in a koi population.
Students use cage test data to explain how an added gene changed traits in mosquitoes.
Students compare what artificial selection and genetic engineering can and cannot do.

How to use

Read the passage together and talk through how to read the two histograms before students start. Part 2 can be a second lesson; finish with the open response as an exit ticket.

Curriculum

NGSS standard covered

MS-LS4-5

Explain how technologies such as artificial selection and genetic engineering change the traits of organisms.

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Red Koi and Glowing Larvae: A Pond Study Day

Compare how people changed the traits of carp and mosquitoes.

Part 1: The koi club's breeding round

Read the passage and the two histograms, then answer questions 1–5.

Pond Study Day at Alder Creek

1Mr. Ewan Achterberg's eighth grade class spent a pond study day at the Alder Creek Nature Center. Students swept dip nets through the cattails and put drops of pond water under microscopes. Paloma Szabo found water fleas, green strands of algae and a few mosquito larvae wriggling head down. Next to the wild pond is a small display pond full of koi, with orange, red, white and black patches.

2A guide explained that koi are a colorful kind of common carp. Wild carp are mostly a dull olive-bronze. About 200 years ago, farmers in Japan raised carp in ponds as food and noticed a few fish with red or white patches. They kept those fish and bred them, and over many generations the bright patterns of today's koi appeared. A local koi club still breeds koi and gives young fish to the nature center.

3In 2022 the club raised 200 young koi from its usual parent fish. At six months old, each fish was photographed and scored by the share of its skin covered in red patches. For the next round, the club chose 8 parents only from fish that scored 60% or more. In 2024, it raised 200 young from those parents in the same pond, on the same food, and scored them the same way at the same age.

4After lunch, Dr. Nnamdi Valcourt from the county mosquito control lab spoke to the class. The yellow fever mosquito lays its eggs in small pools of water such as flowerpot saucers and old tires. Only females bite, and they can spread viruses such as dengue and Zika. Male mosquitoes do not bite. The county is testing an engineered strain of this mosquito. Its males carry a gene that scientists built from bacterial and viral DNA. Daughters that inherit the gene die as larvae, while sons survive. The strain also carries a marker gene from a coral that makes larvae glow red under a special microscope light.

5To check the strain, the lab set up two cages, each with 50 regular females. Cage A also got 50 regular males, and Cage B got 50 engineered males. The lab raised 400 eggs from each cage in trays of water and counted the larvae and the adults that came out. Paloma's group looked at the larvae under the special light.

2022 young koi (200 fish, from the club's usual parents)

2024 young koi (200 fish, from parents that scored 60% or more)

Use the two histograms. Count the fish in the 60–80% and 80–100% bars together.

In 2022, % of the young koi scored 60% or more. In 2024, % of the young koi scored 60% or more.

Use the 80–100% bars. The number of young koi in this bar in 2024 was times the number in 2022.

Use paragraph 3. Why did the club raise both rounds of young koi in the same pond, on the same food, and score them at the same age?

A. So a change in red patches would come from the parents the club chose
B. So the parents could teach the 2024 young to show brighter colors
C. So the 2024 fish would eat more of the food and grow larger patches
D. So the pond water would turn the 2024 young koi a deeper red

Which description best explains how the club changed the 2024 histogram?

A. It chose parents with more red, and the young inherited gene versions for more red.
B. It put a gene for red color from another fish into the eggs of the 2024 young.
C. It kept the young fish in brighter sunlight, so their patches turned red.
D. It fed the 2022 fish a red food, and they passed the color on to their young.

Every 2024 parent scored 60% or more, yet 10 of their young scored less than 20%. Which explanation fits the page best?

A. Those 10 young were photographed at an older age than the other fish.
B. Those 10 young ate a different food from the rest, so their patches faded.
C. The parents also carried gene versions for little red, and a few young inherited many of them.
D. The parents lost red patches before breeding, so some young lost them too.

Part 2: The mosquito cage test

Use paragraphs 4 and 5 and the table to answer questions 6–9.

Cage Test: Young From 400 Eggs per Cage
Cage	Fathers	Larvae counted	Larvae that glow	Adult females	Adult males
A	Regular males	372	0	178	176
B	Engineered males	370	370	0	174

Use the table. The first blank is a number of mosquitoes. In the second blank, round to the nearest whole percent.

Cage B produced fewer adult females than Cage A. Counting females and males together, Cage B produced about % as many adults as Cage A.

Every larva in Cage B glowed, but none in Cage A did. Which explanation fits paragraphs 4 and 5 best?

A. The special light turns on a glow gene that is found in all mosquito larvae.
B. Each Cage B father carried the coral marker gene, and every one of his young inherited it.
C. The Cage B mothers were engineered as well, so they gave their young the glow.
D. The Cage B larvae took in glowing coral cells from the water in their trays.

Suppose the county releases many engineered males in a neighborhood. Based on the cage test, what would most likely happen to the number of biting mosquitoes there over the next few generations?

A. It would likely rise, since Cage B produced more adult males than Cage A did.
B. It would likely fall, since many daughters of engineered males would die as larvae.
C. It would likely fall, since the larvae would glow in the dark water at night and scare off wild females.
D. It would likely rise, since the engineered males would bite people along with the females.

The lab wants to show that the engineered gene, not something about the cages, caused the missing females. Circle the two results that, taken together, are the best evidence.

Cage A, with regular fathers, produced 178 adult females.Paloma found a few mosquito larvae in the wild pond.Cage B, with engineered fathers, produced no adult females.Cage A produced 372 larvae from its 400 eggs.Cage B produced 174 adult males.

Part 3: Comparing the two technologies

Use everything on this page to answer questions 10–12.

10.

Sort each step by the technology it belongs to.

Choosing only koi that scored 60% or more as parentsPutting a coral marker gene into mosquito eggsBreeding the few patched carp that farmers noticed in their pondsBuilding a gene from bacterial and viral DNA for male mosquitoes to carryScoring young fish by their red patches to pick the next parents

Artificial selection	Genetic engineering

11.

Which statement best compares the two technologies on this page?

A. The koi got a gene from another species; the mosquitoes used color variation carp already had.
B. Both technologies changed the animals by changing their food, water and light.
C. The koi changed within one generation; the mosquito strain took about 200 years to build.
D. The koi used patch variation carp already had; the mosquitoes got genes from other organisms.

12.

A visitor says, "If the koi club keeps choosing the reddest fish as parents for many more generations, it will end up with koi that glow red under the special microscope light." Make a claim about this idea. Use evidence from the koi histograms and the mosquito cage test, and explain your reasoning about how each technology changes traits.