Biology (Fossils and evoltion)
- Fosils are the remains or imprints of an organisms from millions of years ago. They provide evidenc of how an organisms changed over time or evolved.
- There are gaps in fossils because organism do not alway form from fossils. Soft-bodied organisms decay and do not leave a trace. Fossils are buried deep underground and haven't been fount yet.
- Limbs of a vertabrates have no common, five-fingered bone pattern called the pentadactyl limb. By recording fossil vertebrates we can see how the pentactyl limb has evolved according to their way of life.
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- Growth can be meausred by the increase in size,length or mass. Health proffessionals use charts called percentile to check the growth of a baby or a child.
- Plants grow by cell division and elongation. It happens in special areas called meristems at the tips of shoots and roots. There are differentiate specualised cells such as leaf cells, root hair cells. Plants continue to grow throughout their lives.
- Animals also grow by cells division and increase in cell size, but stop growing when they become adults.
- In an embryo, stem cells are able to differentiate in to specialised cells as the animal grows. a few stem cells are found in adults but they can only form a limite range of cells.
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- Red blood cells contain pigment called haemoglobin which conbines with oxygen to form oxyhaemoglobin as blood passes through.
- Oxygen is relaeased into respiring tissues. They have a biconcave shape to give them a large surface area to volume ratio so oxygen can easily go in and out. They dont have a nucleus so cant hold the maximum of haemoglobin.
- White blood cells defend the body against diseases in different ways. Some destroy foreign cells in the body. Others produce anitbodies that destroy harmful cells. White blood cells have a nucleus.
- Platelets are tiny cells that help to form blood clots when vessels are damaged. The clot dires and scab to stop microorganisms getting into the damage tissues.
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