TIDES
WHAT ARE TIDES?
- Tides are the periodic variations in the surface water level of the oceans, bays, gulfs and inlets.
- They are the result of the gravitational attraction of the sun and the moon on Earth.
- Tides are important for a large range of animals whether it is fish or birds.
- As the moon orbits the Earth, it's gravity sweeps across the face of our planet. It's power drags a great bulge of oceanic water in it's wake.
- Tides occur every day of the year (every 6 hours).
- The weakest tides of the earth are located near the equator, and the largest tides are in the Bay of Fundy in Nova Scotia.
What causes tides?
- As the moon orbiststhe Earth it's gravity sweeps across the face of our planet. It's power drags a great bulge of oceanic water in it's wake.
Spring and Neap Tides
Spring Tides:
- Approximately twice a month, around new moon and full moon when the sun, moon and earth form a line, the tidal force due to the sun reinforces that due to the moon, the tide's range is then at its maximun.
Neap Tides:
- At first quarter or third quarter of the moon, when the sun and the moon are separated by 90° from the earth view, it is a Neap Tide
Lunar Tides
- The tides occur about an hour later each day. When the moon passes overhead about an hour later each day.
three species
Sand-bubbler Crab
- They normally live in the tropics.
- Sand bubbler crabs are crabs of the genera Scopimera and Dotilla in the family.
- They are small crabs that live on sandy beaches in the tropical Indo-Pacific; during the low time,they form inflated sand pellets which are destroyed by the incoming high tide.
- It hunts meiofauna out in the sand.
- Just a centimetre across works at breakneck speed, filtering out the meiofauna and kicking aside the waste.
- They are really small, around 1cm across the carapase, and they are characterised by the presence of "gas windows" on the merus of the legs.
Jellyfish
- They swim towards the sunlight in the ocean.
- Jellyfish are the major non-polyp form of individuals of the Phylum Cnidaria.
- They are typified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell and trailing tentacles.
- Most of them don't have specialized digestive, osmoregulatory, central nervous, respiratory, or circulatory systems.
- Most jellyfish alternate between polyp and medusa generations during their life cycle.
- Jellyfish reproduce both sexually and asexually.
- Pulsating jellyfish and their swim pals stir up the oceans with as much vigor as tides and winds.
- The shape of the aquatic blobs affects their mixing abilities.
- They are carnivorous, they eat plankton, crustaceans, fish eggs, small fish and other jellyfish, ingesting and voiding through the same hole in the middle of the bell.
- They hunt passively usind their tentacles as drift nets.
- Other species of jellyfish are among the most common and important jellyfish predators, some of which specialize in jellies.
Stingrays
- They are a group of rays, which are cartilaginous fishes related to sharks.
- They are suborder Myliobatiodei of the order myliobatiformes, and consist of eight families.
- Most stingrays have one or more barded stings on thir tail, which are used exclusively in self-defense. the stinger may reach a length of approximately 35 cm and it's underside has two grooves with venon glands.
- Stingrays are usually very docile and curious, their usual reaction being to flee any disturbance, but they will sometimes brush their fins past any new object they encounter.
- When a male is courting a female, he will follow her closely, biting at her pectoral dic. Then he places one of his two claspers into her valve.
- Stingrays are ovoviviparous, bearing live young in "litters" of 5 to 13.
- The female holds the embryos in the womb without a placenta. Instead, the embryos absorb nutrients from a yolk sac, and after the sac is depleted, the mother provides uterine "milk".
- Rays have been known to store sperm and not given birth until they decide the timing is right.