My Science School

          There are almost, as many different ways in which insects protect themselves from enemies as there are different insects. Some insects, such as wasps and ants, have powerful stings or are able to shower their attackers with poisonous fluid. The hoverfly does not sting, but its colouring is so like that of a wasp or bee that enemies are very wary of it! Other insects, such as stick insects and praying mantises use camouflage. They look like the leaves and twigs among which they feed.

          In the insect community there exist many different methods of hunting and killing. Some of these methods are short and quick, and others seem to be slow and painful. Some insects do not even have to fight by virtue of their spectacular camouflaged bodies. However, other insects are nearly always vulnerable to predators. Many insects sport particular colors that scare predators away and some insects use venom in order to subdue their prey before feasting on it. There are many more methods of attack and defense to be observed in the insect world, and even the few methods named above do not begin to touch upon the great variety of ways that insects attack others and defend themselves.

          Some insects use irritating sprays to subdue their enemies. For example, ladybugs, bombardier beetles, and blister beetles are just a few insects that are capable of deterring predators with unpleasant fluids. The bombardier beetle keeps a caustic substance within its abdomen at all times. When this beetle’s life is threatened by a predator, it will spray the invader with its caustic fluid. While the injured predator is occupied with the caustic substance, the bombardier beetle will make its getaway.

          Another interesting, and largely unheard of defense tactic employed by some arthropods involves the sacrifice of a limb. Many long-legged insects, such as katydids, walkingsticks and craneflies have easily detachable legs, which they are more than happy to give up to a predator if it means getting away alive. These legs have “fracture points” located at certain joints on the legs. When a leg is pulled by a predator, the leg will become detached, leaving the insect alive and the predator with a modest meal.

          This is different than mimicry or camouflage, though it uses the same principle. Some insects "hide in plain sight" by resembling objects in their environment. A thorn could really be a treehopper; a twig might be a walkingstick, an assassin bug, or a caterpillar; and sometimes a dead leaf turns out to be a katydid, a moth, or even a butterfly. Some caterpillars resemble bird droppings, and others have false eyespots on their wings or body to create an imitation of a predator's head. Often, these guys are the coolest-looking... the details in their appearance astonishing in their accuracy and creativity.

          If there is one thing most of us have in common, it's distaste for foul smells. And the really bad ones can be enough to make you recoil. Ever been at the epicenter of a skunk attack? It's like someone is burning tires directly in your NOSE. Stink bugs have special glands that produce a foul-smelling reek. The caterpillar form of some swallowtail butterflies have glands just behind their heads that, when disturbed, will rear up and release a terrible stench. Darkling beetles will raise their big, black butt in warning when they are threatened, and if you don't pay attention to the warning - will expel acrid, foul-smelling fluid.

          When stink and burning isn't enough, some bugs will hit their attackers with sticky compounds that harden like glue and incapacitate. Some kinds of cockroaches guard their backsides with a slimy anal secretion (those are three words that are just terrible together) that cripples any ants that launch an attack. And there are types of soldier termites that have nozzle-like heads that can spays sticky, immobilizing toxic fluids at attackers as varied as ants, spiders, centipedes, and other predatory arthropods.

WASPS, bees, ants and termites live in large social groups, in which individual insects each have their part to play in the success of the whole colony. These colonies are built around a single egg-laying female, called the queen. The colonies often build large and elaborate homes. Bees make structures containing six-sided cells in which eggs and honey can be safely stored. Ants and termites often build huge mounds, with tunnels and galleries inside, to house the colony.

The true social insects—all ants and termites, and some bees and wasps—comprise 75 percent of the world's insect biomass, according to E.O. Wilson. A colony of social bees can number in the tens of thousands, and hundreds of millions of ants can live together in a supercolony of interconnected nests.

Why have some insects evolved to live in large, cooperative colonies? There's strength in numbers. Social insects gain several advantages over their solitary cousins. Social insects work together to find food and other resources and to communicate their findings to others in the community. They can mount a vigorous defense of their home and resources when under attack.

Social insects also can outcompete other insects, and even larger animals, for territory and food. They can quickly construct a shelter, and expand it as needed, and they can divide chores in a manner that ensures everything gets done expeditiously.

To give an example, think of termites. All termites are eusocial insects. Within a single termite colony, you will find individuals at various stages of the termite life cycle. Generations of termites overlap, and there is a constant supply of new adults prepared to assume responsibility for the colony's care. The community cares for its young cooperatively.

Termite communities are divided into three castes. The reproductive caste is comprised of a king and queen. The soldier caste of both males and females is specially adapted for defending the colony. Soldiers are larger than other termites and are sterile. Finally, the worker caste consists of immature males and females that do all chores: feeding, cleaning, construction, and brood care.

Spiders belong to the class of arachnids, which also includes scorpions, ticks and mites. None of these are insects. They have eight legs, and their bodies are divided into two parts, not three.

Spiders belong to a group of animals called “arachnids”.  Scorpions, mites, and ticks are also part of the arachnid family.  Arachnids are creatures with two body segments, eight legs, no wings or antennae and are not able to chew. Many people think that spiders are insects but they are mistaken since insects have six legs and three main body parts.  Most insects have wings.

Arachnids belong to an even larger group of animals called “arthropods” which also include insects and crustaceans (lobster, crabs, shrimp, and barnacles).  This is the largest group in the animal kingdom! Approximately 80% of all animals are from this group…that would be over a million different species! There are more than 30 000 different species of spiders.

All spiders are predators and many will eat other spiders.  Scientists have found spiders in amber (Did you watch Jurassic Park?) that dates back to about 2 million years.  Because spider’s skeletons are quite small and fragile it is difficult to find whole fossilized spiders.

Young insects develop in two main ways. In some species, such as grasshoppers and locusts, the young that hatch from eggs look rather like small adults, and are called nymphs. As they grow, the nymphs shed their skins, looking more and more like adults each time.

Other insects, such as butterflies, bees and beetles, go through a process called metamorphosis. Their eggs hatch into larvae or caterpillars. Later these become a pupa or chrysalis, within which an imago, or adult insect, develops. The larvae may live in a different habitat from the adult and require different foods.

All insects start their life cycle as eggs after which there are two different life cycles that can take place dependent on the insect species. The main difference between the two life cycles is the development of a pupa or complete metamorphosis. One life cycle is called Hemimetabolous and only has three stages, the other type of life cycle is Holometabolous and has four stages. Most insect life cycles have four distinctive stages which can be observed just by looking at the physical condition of the insect.

Hemimetabolous life cycles have three stages – egg, nymph then adult – which form the adult insect out of an incomplete metamorphosis. The nymph hatches out of the egg and feeds on plants or roots underground for an extended period of time. As the nymph grows, it sheds its skin, and in the final growth stage, the skin sheds to reveal wings and a fully formed adult.

Holomeaboleous life cycles have four stages – egg, larvae, pupa then adult – forming the adult insect out of complete metamorphosis. The egg hatches into larvas, which resemble fat, short worms with tiny legs and sheds its skin during new growth. Once the larvae are large enough, they wrap themselves in a hardened shell or cocoon/chrysalis. During this pupa stage the insect is completely contained and does not eat any food. The pupa moves slightly as it grows and once it forms a new shape it breaks out of the shell as a fully formed adult insect.

The most common types of hemimetabolous insects are cicadas, cockroaches, grasshoppers or locusts and the most common types of holomeabolous insects are butterflies, true flies, or beetles.

Most insects have wings at one time or another in their lives, although a very few species, such as fleas, silver-fish, firebrats and springtails, do not. Flying insects have two pairs of wings — forewings and hind wings — although not all of them use both pairs for flying. All insects have a tough outer skeleton, six legs and bodies divided into three distinct parts, but there is enormous variation between insect species. Most insects do have wings. Fleas, lice, silverfish, and firebrats are the only truly wingless insect groups that most of us are familiar with. Most adult insects have two pairs of wings, but they’re not always visible. Often they’re hidden, shortened, or nonfunctional. You can easily see both pairs of clear wings on wasps, bees, ants, and termites. Their wings are held on top of their backs and the back pair is usually smaller than the front pair.

A beetle doesn’t appear to have wings at all, yet the hard outer covering on the back of a beetle is actually a pair of modified wings. The second pair of clear, membranous wings are folded up underneath. When a beetle flies, the wing covers, or elytra, spread apart at the center and the flight wings beneath unfold. It all happens so fast though that you can rarely see it happen.

In moths and butterflies, the forewings and the hindwings are covered with scales that create patterns and colors. Cockroaches, grasshoppers, and crickets have flight wings hidden under a leathery pair of front wing covers that match the rest of the body. Files are the only insect group that has only one pair of functional wings. The hind wings are reduced to small, knobbed structures called halteres that act like little gyroscopes to help the fly keep its balance.

After insects, molluscs form the largest group of animals. Molluscs have soft, muscular bodies, often covered by a protective shell. Some, such as snails, move on a muscular foot, which can be withdrawn into the shell for protection. Other, sea-dwelling molluscs, such as squid and scallops, take in water and squirt it out to jet-propel themselves along.

Mollusc is one of the most diverse groups of animals on the planet, with at least 50,000 living species (and more likely around 200,000). It includes such familiar organisms as snails, octopuses, squid, clams, scallops, oysters, and chitons. Mollusca also includes some lesser known groups like the monoplacophorans, a group once thought to be extinct for millions of years until one was found in 1952 in the deep ocean off the coast of Costa Rica.

Molluscs are a clade of organisms that all have soft bodies which typically have a "head" and a "foot" region. Often their bodies are covered by a hard exoskeleton, as in the shells of snails and clams or the plates of chitons.

A part of almost every ecosystem in the world, molluscs is extremely important members of many ecological communities. They range in distribution from terrestrial mountain tops to the hot vents and cold seeps of the deep sea, and range in size from 20-meter-long giant squid to microscopic aplcophorans, a millimeter or less in length, that live between sand grains.

These creatures have been important to humans throughout history as a source of food, jewelry, tools, and even pets. For example, on the Pacific coast of California, Native Americans consumed large quantities of abalone and especially owl limpets. However, the impact of Native Americans on these Molluscan communities pales by comparison to the overharvesting of some molluscan taxa by the United States in the 1960s and 1970s. Species, whose members once numbered in the millions, now teeter on the verge of extinction. For example, fewer than 100 white abalone remain after several million individuals were captured and sold as meat in the 1970s. Besides having yummy soft parts, molluscs often have desirable hard parts. The shells of some molluscs are considered quite beautiful and valuable. Molluscs can also be nuisances, such as the common garden snail; and molluscs make up a major component of fouling communities both on docks and on the hulls of ships.

Arthropods have skeletons on the outside, which give them several advantages over soft-bodied animals. The skeleton forms a waterproof casing, preventing the body from drying out and allowing the animal to live outside water or damp places. In addition, skeletons on the outside, just like those on the inside, give muscles a firm anchoring point, so that the animal is often stronger than soft-bodied creatures of a similar size.

Unlike mammals, insects are invertebrates, meaning they lack an internal skeleton. Instead, they possess non-living exoskeletons located on the outside of their bodies. This exoskeleton protects the insect's internal organs, prevents it from drying out, attaches to the insect's muscles and allows the insect to gather information about its environment. Understanding these benefits of the exoskeleton helps explain why having a skeleton outside the body makes sense for insects.

Protection & Exoskeletons

Insects are protected by their exoskeletons. This hard outer covering prevents easy access to the more vulnerable internal organs. Underneath the exoskeleton, insects have an epidermal layer similar to human skin. But the exoskeleton forms a kind of armor over the epidermis in much the same way that medieval armor protected the skin and organs of knights in battle. Additionally, the exoskeleton successfully repels parasites, fungi, viruses and other biological invaders so insects can stay safe and healthy.Furthermore, pigments responsible for creating the color patterns on insects that serve to ward off potential predators are produced in the exoskeleton.

Exoskeletons and Their Complex Relationship with Fluids

Insects’ exoskeletons are secreted from their epidermis and form three layers: the endocuticle, the exocuticle and the epicuticle. The epicuticle is the topmost layer and is actually waterproof. The epicuticle's primary role is to help the insect keep in its water so it doesn't dry out. Additionally, the epicuticle stops water from coming into the insect's body, which could drown it. Both feats are accomplished thanks to a layer of waxy molecules inside this layer that form a waterproof barrier. Because the exoskeleton is made from a carbohydrate substance known as chitin, it actually stays moist on its own.

Muscle Attachment & the Exoskeleton

In humans and other mammals, muscles do not attach directly to bones. Instead, they are connected via tendons and ligaments. In insects, however, muscles are directly attached to their exoskeletons. Because the exoskeleton is not a single surface but consists of multiple jointed plates, the insect's muscle movement causes the connected exoskeleton plate to move as well. This muscle/plate movement allows insects to move around. Because of this method, insect muscles have a nearly unlimited area for their attachment, allowing for greater variability in movement.

Although at first sight the man o’ war appears to be a jellyfish, in fact it is made up of a whole colony of polyps, each of which has a particular job to do. Some form stinging tentacles; others digest food; and one large polyp is filled with gas to form the “sail” that allows the man o’ war to float, powered by the wind.

The Portuguese man o’ war, (Physalia physalis) is often called a jellyfish, but is actually a species of siphonophore, a group of animals that are closely related to jellyfish. A siphonophore is unusual in that it is comprised of a colony of specialized, genetically identical individuals called zooids — clones — with various forms and functions, all working together as one. Each of the four specialized parts of a man o’ war is responsible for a specific task, such as floating, capturing prey, feeding, and reproduction. Found mostly in tropical and subtropical seas, men o' war are propelled by winds and ocean currents alone, and sometimes float in legions of 1,000 or more! 

Resembling an 18th-century Portuguese warship under full sail, the man o’ war is recognized by its balloon-like float, which may be blue, violet, or pink and rises up to six inches above the waterline. Lurking below the float are long strands of tentacles and polyps that grow to an average of 30 feet and may extend by as much as 100 feet. The tentacles contain stinging nematocysts, microscopic capsules loaded with coiled, barbed tubes that deliver venom capable of paralyzing and killing small fish and crustaceans. While the man o’ war’s sting is rarely deadly to people, it packs a painful punch and causes welts on exposed skin.

Cnidarians are invertebrates, mainly living in the sea that has a single space inside them where food is digested. A mouth leads from the outside to the space, which is called the coelenteron. Often the mouth is surrounded by tentacles, which help to catch food and pass it into the coelenteron. Corals, sea anemones and jellyfish are all cnidarians. Both corals and sea anemones can look like plants at first sight.

Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column, and some have evolved a shell or a hard exoskeleton. As on land and in the air, marine invertebrates have a large variety of body plans, and have been categorised into over phyla. They make up most of the macroscopic life in the oceans.

The earliest animals were marine invertebrates, that is, vertebrates came later. Animals are multicellular eukaryotes, and are distinguished from plants, algae, and fungi by lacking cell walls. Marine invertebrates are animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column. Some have evolved a shell or a hard exoskeleton.

There are well over fifty thousand different kinds of worm, divided into three main groups. The annelids have bodies that are divided into segments. They include earthworms and leeches. Roundworms, also known as nematodes, do not have segments. Many of these are crop pests, eating plants and making crops prone to diseases. Others are parasites, living on or in other animals, some causing serious diseases in humans. Finally, flatworms also include several parasites, including some with a complicated life cycle that involves them living in two different animal hosts one after the other.

There are about one million species of worm, living in a wide range of habitats. They have a long, thin body, and have no legs. Many worms are parasites that live on or in another animal and use strong mouthparts to feed off that animal. Others are predators, and can move quite quickly. The three main groups are Flatworms, Roundworms, and Segmented Worms.

FLATWORMS

There are about 20,000 species of flatworm. They have a solid, flat body that does not contain blood. Most flatworms are parasitic, but some are free-living.

MARINE FLATWORM: Marine flatworms absorb oxygen through the surface of their very thin, flattened body. They creep along, rippling their body to help them move. Eyespots enable them to find their way around. Most are predators, eating tiny animals with the mouth situated on the underside of their body.

TAPEWORM: Tapeworms are parasites that live in other animals, including humans. They have hooks and suckers on their head to attach themselves to the animal’s gut wall. They have no digestive system but absorb food through the surface of their body. They are hermaphrodites – they produce both eggs and sperm.

ROUNDWORMS

Roundworms, or nematodes, are found almost anywhere and exist in huge numbers. As many of the roundworms are transparent, few people are aware of them. The roundworm has a long, round body that tapers towards the tail. The outer layer, or cuticle, is smooth. Muscles run along its body, but not around it. To move along, the worm contracts these muscles, thrashing backwards and forwards in a single plane, making C or S shapes.

SEGMENTED WORMS

This group divides into earthworms, bristleworms, and leeches. All have segmented bodies. The worms’ bodies are fluid-filled, but the leeches are solid.

EARTHWORM: Earthworms are formed from many segments. Only the gut runs through the whole body from head to tail. Worms have a circulatory system with blood vessels but no heart. The thickened area towards the front of their body secretes mucus, which binds mating worms together and forms a cocoon for eggs.

LEECH: Leeches are parasites that live on the outside of other animals. They have specialized cutting jaws to bite through skin so that they can suck the animal’s blood. Substances in their saliva prevent the blood from clotting and make the bite painless so that the animal is unaware it has been bitten. Leeches move by shifting one sucker forwards and then bringing the other one up behind it.

An invertebrate is an animal without a backbone. More than 90% of all animals are invertebrates. Insects form the largest group of invertebrates. Like millipedes and centipedes, crustaceans and spiders, they are arthropods, with jointed bodies and an outer protective casing. There are also many soft-bodied creatures, such as worms and jellyfish, often living in water or damp areas where sun and air will not dry out their bodies. Molluscs are also soft-bodied, but many of them are protected by an outer shell.

All living things are placed into groups depending on common characteristics. The animal kingdom is informally divided into two groups, the vertebrates and invertebrates. Invertebrates are a group of animals that have no backbone, unlike animals such as reptiles, amphibians, fish, birds and mammals who all have a backbone.

Over 95% of all animals on the earth are invertebrates of one form or another. Invertebrates are found just about everywhere in both terrestrial and aquatic habitats, and include animals ranging from sponges, corals and seastars to insects, crabs and worms, just to name a few. For information on collecting aquatic invertebrates in freshwater environments see the Water-watch site. Over 80% of all invertebrates are grouped into the single phylum Arthropoda that includes spiders, crustaceans, centipedes, millipedes and insects.

Insects are different from most other invertebrates. They are the largest Class of organisms and account for over 75% of all animal species. Insects can be separated from other invertebrates as they generally have 6 legs and conform to a common body plan. This body plan comprises of 3 parts, the head, thorax and abdomen although some parts may be more distinct than others. Particular insect orders may have some structures absent, reduced or greatly modified and some young stages can appear very different from their mature adult form.

Often the easiest way to identify a deciduous tree is to look at the shape of its leaves. The general shape of the tree, the way in which the branches join and the pattern of the bark also give clues, especially in winter when the leaves have fallen.

The starting point for most people when identifying trees species is the leaves. There are three basic leaf types: needles, scales and broadleaf. Most evergreens have needles or scales, while most broadleaf trees are deciduous, meaning they drop their leaves when dormant. However, there are exceptions. Larch has green needles that turn color in fall and drop off the tree. Live oak is an evergreen tree with broad, elliptical leaves.

The shape of a leaf can also give clues when identifying broadleaf tree species. Common leaf identification shapes include ovate (egg shaped), lanceolate (long and narrow), deltoid (triangular), obicular (round) and cordate (heart shaped). There is also the palm-shaped maple leaf and the lobed oak leaf, two of our most recognizable leaf shapes.

Ask most people to describe a tree’s bark and they’ll say “gray” or “brown” and leave it at that. While many tree species indeed have gray bark, some have bark that is cinnamon (mulberry), pure white (birch), silver (beech), greenish white (aspen) or copper (paperbark maple) in color.

There are many variations in texture between different tree species, as well. Bark can be furrowed (cottonwood), scaly (sycamore), peeling (hickory), smooth (beech), shiny (cherry), papery (birch) or warty (hackberry).

Often the color and texture of the bark change as the tree matures. This is most noticeable on the trunk—the oldest part of the tree. Silver maple, for example, will go from smooth and silver to furrowed and gray and black as it grows older, as the photo shows.

Some trees have a distinctive shape. Think of the vaselike habit of an American elm tree or the pyramid silhouette of a sweet gum. In some cases, the habit changes as the tree matures—often becoming more rounded or irregular—but shape can help with identifying younger trees that are grown in open space (as opposed to a wooded setting, which encourages taller, narrower growth).

Some trees have a distinctive shape. Think of the vaselike habit of an American elm tree or the pyramid silhouette of a sweet gum. In some cases, the habit changes as the tree matures—often becoming more rounded or irregular—but shape can help with identifying younger trees that are grown in open space (as opposed to a wooded setting, which encourages taller, narrower growth).

In temperate climates, a tree makes rapid growth in the warm spring and summer months and much slower growth in the autumn and winter. This growth shows in the trunk as a light ring during times of fast growth and a darker ring for slower growth. It is therefore possible to count the pairs of light and dark rings to see how many years the tree has been growing.

If you are curious about the year that a tree was planted, then you are in luck, as there is an easy way to tell! You may have heard of how to identify the age of the tree by the rings within its trunk, but what’s inside the trunk can even tell us about the conditions/environment the tree was exposed to for its full life cycle.  A tree may have experienced drought, excessive rain, fire, insect plagues and disease epidemics, injuries, thinning or air pollution.  This can all be told by the trunk of the tree.

The only way to see the rings on a tree is for the entire horizontal surface of the trunk to be exposed.  After cutting horizontally through the tree, all you need to do is count the dark rings and you’ll know the tree’s age! You can also gain insight into environmental conditions affecting the tree based on the appearance of the rings. The rings could have some alteration to their shape, colour, and thickness.  For example, narrow rings may be due to insects or dry conditions. On the contrary, wide rings may indicate a wet-season or the death of neighbouring vegetation, permitting rapid growth. While this method may only work on dead trees, it is not impossible to date a living tree.

Bisecting a living tree will obviously cause it immediate and irreparable damage. It is often important to identify the age of living trees. Fortunately, this is possible, even if only in a rough way. To do this, you need to multiply the diameter of the tree by its species-specific growth factor. First, you measure the circumference of the trunk in inches.  Next, calculate the diameter and then multiply the diameter by the species’ average growth factor.  Now you will have a rough age of the living tree! Here is a chart for trees and their associated growth factor. Naturally, you will need to know precisely what species you are dealing with, for that you may want to consult a professional- like the highly trained arborists.

Trees produce seeds just as smaller plants do. Their flowers or cones are fertilized by the wind, or insects or birds. But a parent tree takes up large amounts of water from the area around it, and its leaves prevent sunlight from reaching the ground beneath, so it is important that all the seeds do not fall directly beneath the tree. Some trees produce fruits that are eaten by birds or animals and carried far away in their digestive systems. Others bear seeds that have “wings” and can be blown far away by the wind.

Wind pollinator flowers may be small, no petals, and no special colors, odors, or nectar. These plants produce enormous numbers of small pollen grains. For this reason, wind-pollinated plants may be allergens, but seldom are animal-pollinated plants allergenic. Their stigmas may be large and feathery to catch the pollen grains. Insects may visit them to collect pollen, but usually are ineffective pollinators and exert little natural selection on the flowers. Anemophilous, or wind pollinated flowers, are usually small and inconspicuous, and do not possess a scent or produce nectar. The anthers may produce a large number of pollen grains, while the stamens are generally long and protrude out of flower. There are also examples of ambophilous (pollinated by two different classes of pollinators) flowers which are both wind and insect pollinated.

Most conifers and about 12% of the world’s flowering plants are wind-pollinated. Wind pollinated plants include grasses and their cultivated cousins, the cereal crops, many trees, the infamous allergenic ragweeds, and others. All release billions of pollen grains into the air so that a lucky few will hit their targets.

Water pollinated plants are aquatic. Pollen floats on the water’s surface drifting until it contacts flowers. This is called surface hydrophily, but is relatively rare (only 2% of pollination is hydrophily). This water-aided pollination occurs in waterweeds and pondweeds. In a very few cases, pollen travels underwater. Most aquatic plants are insect-pollinated, with flowers that emerge from the water into the air. 

Trees can be divided into two groups. Broad-leaved trees, which may also be deciduous, meaning that they drop their leaves in winter, are flowering plants. Sometimes their flowers are very small and difficult to spot. Conifers, most of which are evergreen, retaining their leaves all year round, are cone-bearers. They have small male cones and larger female cones instead of flowers.

If trees didn’t have flowers there would be no seeds, and if there were no seeds, new trees wouldn’t come up each year. And if new trees didn’t come up each year, there wouldn’t be forests.

Every single tree in the world has flowers, though sometimes they are too small to be seen or are buried so deep in the leaves that nobody can find them. Certain trees have flowers that come before their leaves, so people don’t notice the tiny blooms, which usually are not very colorful.

Certain trees have flowers that have no petals; others are green and appear to be buds of coming leaves unless you look very closely. There are even trees whose flowers are too small to see without a microscope.

Evergreen: Evergreen any plant that retains its leaves through the year and into the following growing season. Many tropical species of broad-leaved flowering plants are evergreen, but in cold-temperate and Arctic areas the evergreens commonly are cone-bearing shrubs or trees (conifers), such as pines and firs. The leaves of evergreens usually are thicker and more leathery than those of deciduous trees (those that shed their leaves in autumn or in the tropical dry season) and often are needlelike or scalelike in cone-bearing trees. A leaf may remain on an evergreen tree for two years or longer and may fall during any season. An evergreen forest may be needle-leaved, as the coniferous forests of the Northern Hemisphere, or broad-leaved, as the temperate rain forests of the Southern Hemisphere and the broad sclerophyll forests (with thickened, hardened foliage resistant to water loss) of coastal areas of the Northern Hemisphere. Most tropical rain forests contain broad-leaved evergreens.