A few notes:
1. Your grammar and sentence structure are excellent. Great work.
2. Even though the integrated task requires a shorter length, I still suggest that students follow a typical three paragraph structure for the essay: introduction, point 1, point 2 Note that I don't really recommend including a conclusion, but you can if you like.
3. The introduction could be something like: "The lecture and reading are both about altruism. The author of the reading claims that altruism (which he says is the opposite of selfishness) can be found in both humans and mammals. He mostly examines the case of the meerkat to prove his point. The lecture challenges the reading. The speaker also examines altruism in humans and animals and concludes that their behavior is not entirely altruistic."
That might be a bit simple, but it's a format that works.
4. For the body paragraphs, try to identify one point and one counter-point to write about in each, and then elaborate on it with details from the reading and the lecture. For example:
Para 1 - the altruistic meerkat stands guard and puts himself in danger vs. the selfish meerkat has a full stomach and is in less danger when he guards the group
Para 2 - altruistic humans share food with strangers and donate organs vs. selfish humans donate organs because they like the public accolades
5. Now, in your question there are really only two points. Your example does seem a bit short... you may find three points and counterpoints on the TOEFL, and you can write three paragraphs instead of two.
6. Don't say "the reading part." Just call it "the reading" or "the article."
Does this help at all? I'm going to send a link to an article that explains this in more detail to you via PM. I'm not permitted to post links because I am a new member. Check it out, please!
:TOEFLresources.com: Step-by-step guides to the test and a free essay evaluation service