I know you aren't finished yet but I've noticed you haven't correctly captioned your images. The norm is Figure 1. Title. I love that you mention dolphins, it immediately makes the chapter more interesting. I have also noticed you have a lot in in-text references missing! Don't forget those!
Maybe you could consider putting your defintions in a table or inside a coloured box? Info on how to do that here. Otherwise an interesting read! Good luck!
In general, the first part of the body text addresses the topic, but the second half wanders off topic as it searches for other causes of sexual motivation.
The Summary/Conclusion in places is problematic e.g., "...psychological theories of sexual motivation have little reference to the effect of hormones?" - really?!
The argument in the Conclusion that delayed parenting by women is indicative that hormones don't play a strong role in sexual motivation is problematic, especially given the earlier citation about how few acts of sexual intercourse result in pregnancy. Ideally, the Conclusion should emphasise practical, take-home key points rather than new arguments.
Of the focus questions in the Overview, only one is directly relevant to addressing the topic (i.e., "What role do hormones play in motivating us to have sex?"). Answers to the rest of the questions can be briefly summarised with links to further information, to allow this chapter to focus on the role of hormones in sexual motivation.
Some brief explanation of what hormones are would help to orient a reader.
An example of how the first part about hormones could be integrated with the second part about other causes of sexual motivaton, consider discussing the role of hormones in different stages of sexual arousal.
Addition of case studies or additional examples could be helpful.
Set up the problem to be solved and tell the listener what the presentation will cover.
Selection and organisation
Focus on content which directly addresses the topic - the effect of hormones on sexual motivation - a fair bit of the content is on related matters (e.g., the functions of hormones and sexual response/motivation as separate constructions)
Basic coverage of theory.
Basic coverage of research. Research coverage was promising, but often not directly related to the target topic.
References are not included.
A Conclusion slide summarising the take-home messages / key points could be helpful.