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LIVING THINGSCYCLE 3ACTIVITY 4WHY DON’T ALLANIMALS’ EGGSLOOK THE SAME?Techniques and instrumentation: Use of simple observational instruments Use of simple measuring instruments Design and manufacture of environmentsAppropriate language: Terminology related to an understandingof living things Drawings, sketchesSUGGESTEDMATERIALSEXPERIMENT OBJECTIVESAND CONTENTThe primary goal of this activity is to give students anopportunity to compare and understand the reasonsfor variations in eggs’ appearance, along with theadaptive strategies of certain egg-laying animals.ALLERGY WARNING: INFORM ALL STUDENTSTHAT IT IS STRICTLY FORBIDDEN TO EATTHE EGGS USED IN THE EXPERIMENTS.ESSENTIALKNOWLEDGEMatter: Characteristics of living things:reproduction of animals Transformations of living things:metamorphosesSystems and interaction: Interaction between living organismsand their environment: adaptationScientific equipment: Scales Magnifying glasses Scalpels Vivarium (optional) Bird egg identification guidesPerishable non-scientific materials: Items from nature(dead leaves, branches, feathers, etc.) Eggs of hens, quails or fish WaterNote: It is important to store eggs in a coolplace so they do not go bad.Household materials: Small jars Food coloring Latex gloves RocksSchool supplies: Paper Colored pencilsSchool equipment: Refrigerator (or cooler)ÉCLAIRS DE SCIENCES GUIDE CYCLE 3 LIVING THINGS1

LIVING THINGSACTIVITY 4CYCLE 3CONTEXT: SITUATIONALPROBLEM OR RESEARCHQUESTIONYou went on a walk with your parents and youwere surprised to see that eggs can have differentshapes and colors: there were white ones, brownones and speckled ones. You thought all eggswere white, and you wonder why eggs don’t alllook the same.SUGGESTED PREPARATORYACTIVITIES (INTRODUCTION)The teacher asks the students to name animalsthat lay eggs. The teacher discusses the differencebetween viviparous animals (which give birth tolive young) and oviparous animals (which lay eggs).Images of eggs or real eggshells could be shownto enrich the discussion. The teacher could thenhave the students think about the reasons that notall eggs look the same.INITIAL IDEASAND HYPOTHESESHere are a few examples of hypotheses the studentsmight formulate based on their initial ideas:Example 1I predict that eggshells from birds protect the embryosfrom rain and microbes. I predict this because shellsare hard, and I think they must be waterproof, becausebird nests are exposed to the rain.Example 2I predict that the color of eggs is a type of camouflage.I predict this because I once saw quail eggs andthey reminded me of little rocks.Example 3I predict that eggs laid in water are soft and eggslaid on land have a shell that prevents them fromdrying out. I predict this because the eggs that myfish lay are soft, while the hen eggs that my parentsbuy at the grocery store are hard.WORK PLAN ANDEXPERIMENTATIONHere are a few examples of experiments the studentscan carry out to verify their hypotheses:Example AThe students verify whether the shell of a hen’s eggprotects the inside of the egg. They weigh two hen’seggs before the experiment and fill two small jarswith clear water. They add food coloring to one ofthe jars and then place an egg in each containerand wait 24 hours. They remove the eggs from thewater, dry the shell and weigh them again to see ifany water got inside the shell. They then break theeggs and make color sketches of their observations.Is the internal and external appearance of the eggsthe same?Note: After breaking the egg, it would be interestingfor the students to observe the air cell, which is asmall cavity in the large end of the egg.RECORD ALL YOUR IDEAS AND OBSERVATIONSIN YOUR EXPERIMENT WORKBOOK.2ÉCLAIRS DE SCIENCES GUIDE CYCLE 3 LIVING THINGS

LIVING THINGSACTIVITY 4Example BThe students check to see if there is a link betweenthe appearance of birds’ eggs and where they arelaid. They try to imagine what the eggs look like ofbirds such as the downy woodpecker, the ring-billedgull or the red-winged blackbird by observing theenvironment in which these species live. The studentscan disguise hen’s eggs by adding marks and colors,use quail eggs, or draw the eggs on paper. Next,they reproduce the environments where these birdslay their eggs: tree cavities, stony shorelines, nestsin low-growing wetland vegetation. They can recreatethese environments using items from nature or bydrawing them. Then they validate their results bydoing research.Note: The students can do the same experimentwith insect eggs such as those of lady bugs, whichare larger than most insect eggs.Example CThe students compare bird eggs, which havehard shells, with fish eggs, which have a softmembrane. They observe the two types of eggsunder a microscope, drawing sketches to recordtheir external appearance, texture and color, thendissect the eggs to observe their internal parts.They allow a hen’s egg and several fish eggs todry out for 24 hours and record the changesin appearance.Note: The students should use latex gloves inorder to avoid any possible contact with bacteria.CYCLE 3EXPERIMENTAL FACTORSTo ensure scientific rigor, the students should evaluatethe experimental factors that might influence theexperimental results. Amount of food coloring used Amount of water used Quality of eggs (cracks) Precision of measurements Variety of specimens Level of humidity Water temperatureDISCUSSION: SUGGESTEDINTEGRATION ACTIVITIES(CONSOLIDATION)The teacher has the students present theirexperimental results and their sketches in theform of egg-shaped posters. The activity canbe enriched by showing diagrams of the eggsof hens, reptiles, amphibians, fish, and insects.The students could work together on a summarytable of the different survival strategies ofegg-laying animals.SUGGESTED ACTIVITIESFOR APPLYING KNOWLEDGE(APPLICATION)The teacher asks the students to create a GuinnessBook of Records type book entitled Eggcelent Eggs,in which each student presents a record concerningeggs (e.g., largest bird egg, fish that lays the mosteggs, strange insect eggs, and other surprising facts).To conclude, the students could start a project tohatch eggs of an egg-laying animal in order to observeits life cycle.ÉCLAIRS DE SCIENCES GUIDE CYCLE 3 LIVING THINGS3

LIVING THINGSACTIVITY 4CYCLE 3SCIENTIFIC CONCEPTUALCONTENTOviparous versus viviparousMany groups of animals such as insects, fish,amphibians, reptiles, and birds reproduce by layingeggs. These are called oviparous animals. Eggs protectthe embryos and provide nutrition required fordevelopment. Eggs are fertilized ovules that areformed in female reproductive organs called ovaries.The fertilization of ovules can be internal or external,depending on the species. The hen’s eggs we eatare in fact ovules, since they have not been fertilized.Mammals, on the other hand, are viviparous, i.e., theirembryos develop inside the mother’s body. There arealso animals, called ovoviviparous, whose reproductivesystems share elements of both oviparity and viviparity,i.e., the eggs are incubated and hatch within thefemales’ reproductive tract. This uncommon strategyis employed by certain reptiles, insects and fish.Sharks are also ovoviviparous.Egg adaptationsAnimals that are well adapted to their environmenthave better chances of survival. Survival strategiesfor oviparous animals include laying a large number ofeggs (insects, fish, amphibians), laying simultaneously(all females of the species lay at the same time,e.g., sea turtles), camouflaging the eggs (buryingthem, hiding them in vegetation, etc.), camouflagingthe nest, and laying eggs that blend intothe environment.4ÉCLAIRS DE SCIENCES GUIDE CYCLE 3 LIVING THINGSInsectsMost insects lay eggs. These eggs are surrounded bya shell that prevents them from drying out. The eggshatch into larvae that become adults after varioustransformations. Some species pass through oneor several stages of metamorphosis, which may becomplete (egg, larva, pupa, adult [also called imago])or incomplete (egg, nymph, adult). Insects thatundergo incomplete metamorphosis are said toreach the adult, or “imago” stage, when they areable to reproduce. Insects lay their eggs in diverseenvironments, ranging from on the ground, in water,on plants or tree bark, or on decomposing matter.They are tiny and usually numerous, ranging fromhundreds to thousands, depending on the species.However there are several exceptions, such asaphids. When “baby” aphids are born, they alreadyresemble adults.FishMost female fish lay a great number of eggs in thewater – up to millions per laying. The eggs have asoft membrane, which contains the vitellus (yolk),the dark part of the egg that serves as a nutritionalreserve, and the blastodisc, which becomes the fishlarva. Only a few eggs will develop to the adult stage,since many will be eaten by predators or will diebecause of inadequate environmental conditions suchas temperature or oxygen concentration.AmphibiansAmphibian eggs are laid in water or wetlands.They are gelatinous and lack a shell, making themvery permeable. Because of this, they are verysensitive to pollution, which explains in part whyamphibian populations are declining worldwide.When they hatch, the larva survives on the foodreserves of the vitellus. They undergo metamorphosisbefore becoming adults (e.g., tadpoles).