CBSE Class 12-science Answered

Hi Srishti,

• Evo devo stands for evolutionary developmental biology. This field of study encompasses many different ideas. The foundation of the field is based on the gene level of inheritance which leads to microevolution.
• As an embryo develops, certain genes need to be activated in order for the traits carried on that gene to be expressed. Most of the time, there are biological clues for these genes to turn on based on the age of the embryo. Sometimes, environmental conditions can trigger the expression of the developmental genes as well.
• Evo devo theory of evolution explains the idea that all life on Earth came from a common ancestor. This common ancestor had the exact same genes we see today in all of our modern species. It is not the genes that have evolved over time. Instead, it is how and when (and if) those genes are expressed that has evolved.
• Natural Selection is the mechanism that chooses which of these ancient genes are expressed and ultimately how they are expressed. Over time, the differences in gene expression led to the great diversity and large numbers of different species we see in the world today.
• The theory of evo devo also explains why so few genes can create so many complex organisms. It turns out that the same genes are used over and over again, but in different ways. The genes that are expressed to create arms in humans may also be used to create legs or even a human heart. Therefore, it is more important how the genes are expressed than how many genes are present. Developmental genes across species are the same and can be expressed in a nearly unlimited number of ways.