Sexual Selection and Showy Traits

Teach the evidence sheets first, starting with the brains and embryos, then the fossil timelines. Finish with the data sheets on mice, anoles and beetles so students see selection happen in numbers.

Read Andersson's long tailed widowbird experiment and compare natural and sexual selection. The directions on the page read: Read the text and study the bar chart. Then answer the questions on page 2. An answer key is included.

Yes, both. We made it for 8th grade living things, and it works the same at home or at school. At home, a student can work through it alone and then go over it with you, which shows quickly what is solid and what needs another look. In class it works as independent practice, homework or a warm-up, and you can print one copy or a full set.

A vestigial structure is a body part that is much smaller or less used than the same part in related animals. Python hip bones, the human tailbone and kiwi wings are examples. Vestigial Structures as Evidence of Ancestry asks what each part suggests about ancestors.

Sexual selection spreads traits that help an animal win mates, even when those traits make survival harder. Sexual Selection and Showy Traits follows a field experiment with long-tailed widowbirds in which males with lengthened tails gained the most new nests.

Track how common a trait or allele is over several generations and graph it. Rock Pocket Mouse Fur Color Over Generations graphs dark mice on lava and on sand, and Calculate Allele Percents in a Beetle Population counts alleles in 100 beetles each generation.