You probably never thought that an animal could live without a head, heart, or bones. In fact, this species existed 500 million years ago and exists to this day, in addition they are considered “cousins” of the ancestors of many species of vertebrates today. The vertebrate family of today is extremely prosperous, with more than 60,000 members, all of them with different looks, habits and temperament, but this “cousin” has only one child. Only alive, they are called Amphioxus – Van Xuong fish, this species is also considered living fossils. Although Van Xuong fish is called fish and at first glance it is very similar to fish, it is not actually fish. On our planet today, most animals that exist are vertebrates, such as horses, cattle, sheep, chickens, dogs, cats, tigers, ba … Of course, there are us as well. What makes this particular “fish” so exotic and unlike any fish is that they are vertebrates, have no vertebrates but are still grouped with vertebrates, cord animals and form the Chordate branch. Biologists believe that Van Xuong fish are animals during the transition from invertebrates to vertebrates, today they are considered to be the ancestors of fish, but they are completely not fish. The skin layer of Van Xuong fish has 2 main layers, the outer epidermis and the dermis on the inside. Unlike most vertebrates, their epidermis has only 1 cell layer, while the epidermis is underdeveloped, mainly composed of colloid or elastic connective tissue. There are more than 66,000 species of animals in the order Phylum Chordata. The most remarkable thing is that vertebrates make up the largest proportion, with more than 66,000 species, the main caudal subsector is the sea level, and there are currently about 3,000 known species; and head vertebrates, only two families of fish Van Xuong and fish Asymmetron – there are 30 species. In fact, the skeleton of this fish is the wire that runs along the body and back from the tail to the head. The gill region, the skeleton, is a network of horizontal and vertical interconnected rods. The fins and tentacles are also supported by the connecting rod. Their central nervous system is a neural tube running along the body, located above the spinal cord but not reaching the end of the spinal cord, wrapped in a protective glue film. Although the Van Xuong looks like a fish, the biggest difference between it and its vertebrates is that it does not have a real head, sensory organs such as smell, sight and hearing, even a skull. The teeth are also something too fictional for them. This animal has only a bunch of elastic “legs” on the head to play the role of supporting the body. The most amazing thing is that it doesn’t even have a heart; instead, it relies on the beat of part of the blood vessel to carry blood. Their musculoskeletal system is less dissociated and typical dissociated. Therefore, muscles can only ensure simple bending movements, consistent with the lifestyle of being buried in the sand. The muscular system consists of many muscles (myomera), arranged from the front end to the posterior end of the body. The muscle segments are intersected by septum by connective tissue (myosepta). The muscles on both sides of the body are arranged alternately with comb teeth together. As a result, when swimming, the Pangasius swim, its body bends along the horizontal plane. Amphioxus is widely distributed in the shallow waters of the ocean, and Qingdao and Xiamen in China are their primary habitats. In addition, there are coasts of Southeast Asia and coasts of California and Florida, Norway, the Mediterranean and Africa. Due to its rich nutrition and delicious taste, Van Xuong fish is considered a delicious traditional dish in Southeast Asia. Van Xuong fish is 3 to 5cm long, the morphology is very strange. The long and flattened body looks almost like a burden. The whole body color is pink, semi-transparent, the parallel longitudinal muscle fibers can be seen. They have no scales, no fins, no vertebrae, and their internal organs are just a rhythmic, rhythmic, complex. No senses like eyes, nose, or ears. There is no differentiation to the digestive tract. Apart from the mouth and throat, just a piece of intestine that leads straight to the anus. Van Xuong fish often follows tidal water to swim in estuaries where the seabed is shallow, almost unable to defend themselves but capable of penetrating into the ground. Their lifespan is about 3-4 years, they often bury half of themselves in the sand, while the other half is exposed to the plankton from the river. Their muscles are less differentiated, so they can only move in water by simple bending movements. When not moving they often bury themselves in the sand. The way of respiration of Van Xuong fish is similar to that of fish. They vibrate to inject capillaries (mouth tassels) to carry the stream of water from the gill slits. The wall of the gill slot has many blood vessels, where gas exchange occurs.

12th grade students AT.1 Gia Dinh High School in Biology class. Illustration Ecology (Biology grade 12) is the part with close knowledge, easy to deduce, so it can be called “easy”. However, the amount of knowledge in this section is very much, so if not codified, it will be “difficult”. Ecology section consists of 3 chapters, 11 lessons, students need to systematize knowledge and understand ecological terms. Specifically in Lesson 35 Habitat and ecological factors , in Chapter I Individuals and biomes , students need the system of ecological factors to include Infertility factor (physical factor and chemical factor) and the existential factor (the organic world and the relationship between organisms). The example in the reference year 2021 Question 87: Which of the following ecological factors is the infertility factor? A. Worm. B. Light. C. Worms that eat rice leaves. D. Rice plants. We can easily know that answers A, C, D belong to the existential factor, and answer B is the physical factor – the infertility factor. Besides, we need to understand about ecological limit and ecological drive. In the ecological limit, it is necessary to know the tolerance interval, the favorable interval, the lethal point, the positive point and we can adopt the example of the ecological limit of Tilapia for easier understanding. Students need to be able to distinguish ecological drive and accommodation to avoid confusion we can remember accommodation is just a place of residence still Ecological drive shows the way that species lives. Next, we need to note about the adaptation of the organism to temperature, it is necessary to understand the two Principles of Becman and Alen. Becman’s Rule tells us that “Thermostats live in temperate regions larger body size compared with animals of the same species or closely related species living in warm tropics. We can remember quickly “Body size: animals in temperate> tropical animals”. About the Anlen rule “ Tropical animals that live in temperate regions have ears, tails, and limbs usually smaller ears, tails, and limbs of similar animals living in hot regions ”. Can remember quickly “ Sizing of parts: tropical animals> temperate animals “. Students in grade 12AT.1, Gia Dinh High School are making mind maps for lesson 35 One of the content that frequently appears in the exam is Lesson 40 Biomes and some basic features of biomes. First of all, they need a system of relationships between species in a community. Example from 2021 references Question 89: In biomes, which of the following ecological relationships belong to the supportive relationship between species. A. Parasites. B. Inhibition – sensitization. C. Competition. D. Symbiosis. When the systematization is easy, we can immediately choose the answer D. At the same time, it is necessary to understand relationship forms and take illustrative examples to easily remember. Test papers often give specific examples asking what relationship it is? Example from 2021 references Question 95: During the breeding season, females in the stork population compete for a favorable place to nest. Here’s an example of a relationship A. competing for the same species. B. supporting the same species. C. Assembly. D. cooperation. Based on the title “female individuals in the stork population” meaning “of the same species”, they “contested”. , We conclude this is an example of a competitive relationship with a species. So for this type of question, we rely on phrases, keywords, and clauses of the question to make inferences. The next and most frequently appearing examples on the test are food chains and food webs. Regarding the food chain, we need to note that there are two types of food chains: the food chain starts from the autotrophic organism and the food chain starts from the organic humus decomposing organism. In food chains and webs, it is easy to confuse the “number” between the nutrient level and the consuming organism. Illustration : Floating plants -> Invertebrates -> Small fish -> Large fish Floating plants are organisms that produce a level 1 nutrient Invertebrates are a primary consumer but are a tier 2 nutrient. Small fish is a tier 2 consumer but is a tier 3 nutrient. Larger fish are tertiary consumers but are a level 4 consumer. Example from 2021 references Question 103: Feeding the food chain: Rice plants Deep eating rice leaves Field frog Hawthorn cobra. In this food chain, which organism belongs to the tertiary consumer group? A. The hawk. B. The bronze frog. C. Worms that eat rice leaves. D. Cobra. With a clear understanding and clear knowledge system, it is easy to identify the Cobra as a third-order consumer. Through basic analysis of the above contents, we easily recognize one thing: Knowledge of Ecology is not difficult, just systematized by mind maps, images, tables, … then we easily solve the questions in the exam. Please plan to systematize your knowledge with mind maps for the Ecology section to do well the 7 questions of Ecology in the high school graduation exam. Based on the 2021 high school graduation exam illustrative exam questions, we can see that the Genetic Mechanism and Variation 9 sentences (with 1 sentence of high application), The genetic rule has 10 sentences (4 sentences with high volatility 2-sentence population genetics (1 sentence highly manipulated), 1-sentence application of genetics, 1-sentence Genealogy genetics, 6-sentence evolution (1 sentence to apply), 7-sentence ecology (1 sentence and Biology in Grade 11 has 4 sentences. Thus, basic knowledge is 7.5 points, applying 1.5 points low and applying 1 point high. We can see that the content of Biology subject with a huge amount of knowledge, to facilitate learning and review students need to systematize knowledge is essential. If students have a clear study and study plan, scoring 7-8 is entirely possible.

Professor Chris Buddle of the Department of Insect Ecology at McGill University, Canada pointed out that: “Out of nearly 40,000 species of spiders in the world, only about 10 can be dangerous to humans. Even venomous species are very unlikely to come into contact with humans, let alone attack us. ” Are spiders any color? It sounds strange, but spiders don’t really have blood. What they have is called “Hemolymph”. In fact, our blood is based on iron-containing hemoglobin molecules, so they are red. However, the blood of the spider is based on the protein called Hemocyanin derived from copper. This hemocyanin has a fairly clear color, but when exposed to oxygen it turns dark blue. Spiders cannot digest food in solid form They have to pump a liquid into their prey to soften their internal organs and tissues. After everything is softened completely, spiders can suck the contents inside to nourish their bodies. Spiders can control their blood pressure while on the move Spiders not only use muscles to move, but they also know how to combine blood pressure to walk or jump, depending on the species. Spiders contract muscles in the nipples and increase hemolymph pressure in the legs, which makes it easier for them to expand the area of ​​movement. This sudden increase in pressure also caused their legs to leap in different directions. Spiders have no vertebrae Spiders have no bones. They have only a set of sclera surrounding the organs and blood. This makes them classified as invertebrates or non-vertebrates. However, spiders are not the only species with sclera. Practically all insects and arachnids have that set of sclera. Having a set of sclera allows these organisms to grow more and periodically they need to “strip off” or replace their sheath. They can also re-develop the body in a short time. All invertebrates (even spiders) are very vulnerable before their sclera can harden. There is a species of spider that actually lives in the water There is a species of spider that is adapted to live in water, also known as the “Diving Bell” spider. Special soft hairs surround their bodies in the shape of air bubbles that provide oxygen in this particular habitat. Spiders are also a vegetarian Bagheera Kiplingi Spider (Kipling Spider) was discovered in the 1800s, their main food is acacia buds and plants. Sometimes this spider also eats larvae. It is also the only vegetarian spider in the world. Spiders will eat back their old spider silk When the silk loses its cohesion or becomes too dirty, the spiders often eat it and use nutrients from the old silk to create a new web. Do you see ? The spiders recycle them… in their own way. Antarctica has no spiders. Antarctica is inhabited by spiders. These are simply places where the climate is so extremely cold that they cannot do the usual metabolic processes. N What will poisonous bites look like? However, you should still be aware of some spiders with venom that carry extremely dangerous venom. The red back spider in Australia has a venom that causes nerve damage to humans for 24 hours. The black widow spider is famous for its poisonous bite, affecting the relatively strong nervous system, but it is difficult to cause death. When biting the spider spider, the wound becomes infected, leading to blood infection and gangrene. Tarantula large black spider in the rainforest will make people fall into a coma immediately. 6-eyed sand spider will cause local clotting and wound necrosis.