Many animal species spend the first part of their lives developing in eggs, including birds, reptiles, fish, amphibians, and invertebrates. Over time, species adapted to lay eggs or give live birth depending on what would be more beneficial to their survival. For example, birds would have a much harder time flying and finding food if they carried baby birds in their bellies, so it helps them to lay eggs instead.
If you have seen fish eggs before, you may have noticed how different they are from the chicken eggs in the grocery store. All eggs are unique to each individual species. Each egg needs to be perfect for the conditions that it is laid in. Millions of years ago when life only lived in the sea, the earliest eggs were laid in water with thick jelly just like frogs or fish eggs, but some eggs adapted to be better on land as animals moved to dryer habitats. Eggshells (for land species) have calcium in them which allows the egg to harden. These eggs, such as chicken eggs, protect the embryo (baby animal) inside from disease and threats.
Once an egg is laid it can take from a few days or even weeks to hatch depending on the species. During this time, the embryo grows from a single cell to a baby animal ready to hatch. Embryos use the nutrients inside the egg to help them grow.
Activity Time: Spongy Moth Egg Hunt
One species that lays eggs in the biosphere region is the spongy moth. The spongy moth is an invasive species that defoliates trees, sometimes killing them. One thing you can do to help protect trees from the spongy moth, is collect and destroy the eggs before they hatch.
Here’s how you can protect your favourite trees:
- Find a bucket that will be able to hold the egg sacs
- Look closely at each tree on your property or nearby and you will see light brown fuzzy-looking sacs on the tree
- Use a butter knife or a popsicle stick to scrape the eggs off the tree into the bucket *Do not do it on a windy day as sacs will blow away and spread*
- Mix the eggs with soapy water and leave it for few days
- Dispose of the contents down a drain