Dive into the fascinating world of invertebrates - animals without... Show more
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LeeLee Naquin
11/29/2025
Biology
Invertebrates Basics Notes
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Nov 29, 2025
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Comprehensive Invertebrates Study Notes
LeeLee Naquin
@leeleenaquin_ptsq
1 / 3
Invertebrate Basics & Body Symmetry
Invertebrates are animals that do not have backbones, making them fundamentally different from vertebrates like mammals, birds, and fish. Understanding these creatures starts with recognizing their body symmetry patterns.
Animals display three main types of symmetry. Asymmetrical animals lack organized symmetry altogether. Animals with radial symmetry have body parts arranged in a circular pattern around a central point (like a bicycle wheel). Those with bilateral symmetry can be divided into matching halves along a central plane (like your left and right sides).
Two important invertebrate phyla with distinctive features are Porifera and Cnidaria. Porifera (sponges) are sessile animals, meaning they cannot move from place to place. Cnidarians include jellyfish and sea anemones, which protect themselves using stinging tentacles and display radial symmetry.
Fun Fact: Cnidarians like jellyfish have specialized stinging cells called nematocysts that can fire like tiny harpoons when triggered by touch!
Worms and Mollusks
The world of worms includes three distinct phyla with unique characteristics. Platyhelminthes (flatworms) lack a circulatory system and rely on diffusion to distribute nutrients. Some, like tapeworms, are dangerous parasites. Nematoda (roundworms) are mostly free-moving organisms that can spread through unwashed hands or raw fish. Annelida stand out with their segmented bodies and include familiar creatures like earthworms and leeches.
Mollusks form another fascinating phylum defined by their soft bodies and shells. All mollusks display bilateral symmetry but are divided into distinct classes. Gastropods are shelled mollusks like snails. Bivalves have distinctive hinged shells and include clams and oysters. Cephalopods (like octopuses) have long tentacles for catching prey and can squirt ink to confuse predators.
Cephalopods display remarkable adaptability, including the ability to manipulate skin colors for camouflage, making them among the most intelligent invertebrates.
Amazing Adaptation: Octopuses can change both the color AND texture of their skin to blend perfectly with their surroundings in less than a second!
Echinoderms and Arthropods
Echinoderms include sea stars, sand dollars, and sea urchins. Despite their adult radial symmetry, many echinoderms begin life with bilateral symmetry before transforming as they mature.
The phylum Arthropoda (meaning "jointed feet") is the largest animal group on Earth. These creatures have segmented bodies with smaller sections fused into larger body regions. They're protected by an exoskeleton that provides support and protection but requires them to molt as they grow.
Arthropods are divided into several classes with distinct features. Arachnids (like spiders) have eight legs total. Crustaceans include shrimp, crabs, and lobsters, which must periodically shed their rigid exoskeletons to grow. Insects are distinguished by having exactly six legs - a key difference from arachnids.
Did You Know? The total weight of all ants on Earth is roughly equal to the total weight of all humans! Arthropods truly dominate our planet by numbers and biomass.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Comprehensive Invertebrates Study Notes
LeeLee Naquin
@leeleenaquin_ptsq
Dive into the fascinating world of invertebrates - animals without backbones that make up about 97% of all animal species on Earth! These creatures come in incredible varieties with different body structures, survival adaptations, and habitats that we'll explore through... Show more
Invertebrate Basics & Body Symmetry
Invertebrates are animals that do not have backbones, making them fundamentally different from vertebrates like mammals, birds, and fish. Understanding these creatures starts with recognizing their body symmetry patterns.
Animals display three main types of symmetry. Asymmetrical animals lack organized symmetry altogether. Animals with radial symmetry have body parts arranged in a circular pattern around a central point (like a bicycle wheel). Those with bilateral symmetry can be divided into matching halves along a central plane (like your left and right sides).
Two important invertebrate phyla with distinctive features are Porifera and Cnidaria. Porifera (sponges) are sessile animals, meaning they cannot move from place to place. Cnidarians include jellyfish and sea anemones, which protect themselves using stinging tentacles and display radial symmetry.
Fun Fact: Cnidarians like jellyfish have specialized stinging cells called nematocysts that can fire like tiny harpoons when triggered by touch!
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Worms and Mollusks
The world of worms includes three distinct phyla with unique characteristics. Platyhelminthes (flatworms) lack a circulatory system and rely on diffusion to distribute nutrients. Some, like tapeworms, are dangerous parasites. Nematoda (roundworms) are mostly free-moving organisms that can spread through unwashed hands or raw fish. Annelida stand out with their segmented bodies and include familiar creatures like earthworms and leeches.
Mollusks form another fascinating phylum defined by their soft bodies and shells. All mollusks display bilateral symmetry but are divided into distinct classes. Gastropods are shelled mollusks like snails. Bivalves have distinctive hinged shells and include clams and oysters. Cephalopods (like octopuses) have long tentacles for catching prey and can squirt ink to confuse predators.
Cephalopods display remarkable adaptability, including the ability to manipulate skin colors for camouflage, making them among the most intelligent invertebrates.
Amazing Adaptation: Octopuses can change both the color AND texture of their skin to blend perfectly with their surroundings in less than a second!
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Echinoderms and Arthropods
Echinoderms include sea stars, sand dollars, and sea urchins. Despite their adult radial symmetry, many echinoderms begin life with bilateral symmetry before transforming as they mature.
The phylum Arthropoda (meaning "jointed feet") is the largest animal group on Earth. These creatures have segmented bodies with smaller sections fused into larger body regions. They're protected by an exoskeleton that provides support and protection but requires them to molt as they grow.
Arthropods are divided into several classes with distinct features. Arachnids (like spiders) have eight legs total. Crustaceans include shrimp, crabs, and lobsters, which must periodically shed their rigid exoskeletons to grow. Insects are distinguished by having exactly six legs - a key difference from arachnids.
Did You Know? The total weight of all ants on Earth is roughly equal to the total weight of all humans! Arthropods truly dominate our planet by numbers and biomass.
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user