Answer: Imagine life without your best friend. Who would you hang out with and talk to about your problems? Life would be so lonely! You rely on your friends for companionship, fun, and support. Animals rely on each other, too. Some have lifelong relationships with other organisms, called symbiotic relationships. There are three different types of symbiotic relationships: mutualism, commensalism, and parasitism.
Mutualism: both partners benefit. An example of mutualism is the relationship between the Egyptian plover and the crocodile. In the tropical regions of Africa, the crocodile lies with its mouth open. The plover flies into its mouth and feeds on bits of decaying meat stuck in the crocodile’s teeth. The crocodile does not eat the plover. Instead, he appreciates the dental work. The plover eats a meal and the crocodile gets his teeth cleaned. Coincidentally, the Egyptian plover is also known as the crocodile bird.
Commensalism: only one species benefits while the other is neither helped nor harmed. For example, remora fish are very bony and have a dorsal fin (the fin on the back of fish) that acts like a suction cup. Remora fish use this fin to attach themselves to whales, sharks, or rays and eat the scraps their hosts leave behind. The remora fish gets a meal, while its host gets nothing. Selfish, sure, but neither gets hurt.
Parasitism: One organism (the parasite) gains, while the other (the host) suffers. The deer tick is a parasite. It attaches to a warmblooded animal and feeds on its blood. Ticks need blood at every stage of their life cycle. They also carry Lyme disease, an illness that can cause joint damage, heart complications, and kidney problems. The tick benefits from eating the animal's blood. Unfortunately, the animal suffers from the loss of blood and nutrients and may get sick.
B. Salmon envolved before kangaroos
1. Rhythm generators (SA node)
2. Conductive cells (node cells)
3. Contractile cells (myocardial cells)
Answer:
Homologous structures
Explanation:
Features that are similar in structure, but appear in different organisms and may have different functions
