Other mistake: During the opening scene, basic explosive physics dictates that the car should have moved away from the meteor crash, not up and over it.
Factual error: When the army starts blowing the napalm early, you see the tent explode. Ira and his group were standing next to the meteor and the tent was exactly over the meteor. They should be dead.
Continuity mistake: When Julienne Moore's character trips over, from the distant shot she gets up onto her hands and knees, then when her garter is seen, she is lying flat on the floor again.
Continuity mistake: When Ira and Harry arrive at the impact site Wayne is desperate to get to his fireman training exam. Cut to the next scene, Ira is working late at night, and then shows Harry their 'discovery'. Cut to the next scene, its daylight and Wayne is doing his test.
Plot hole: Because humans have a layer of subcutaneous fat under the skin, the bug that travels under Harry's skin would have caused not only significant damage but an amazing amount of pain while moving around. There would have also been severe internal damage caused by the bug if it traveled into his colon where they ended up removing it from.
Factual error: Ira says the aliens have 10 base pairs in their DNA and humans have 4 base pairs. Humans have four bases in their DNA, not 4 base pairs (we have over 3 billion base pairs). Not a mistake a biologist would make.
Other mistake: The puffy small burst explosions that occur within the cave do not exhibit how napalm would detonate, especially with the amount used, method they are detonating it and sheer scale of what they were looking to accomplish by destroying the alien habitat.
Deliberate mistake: The energy the meteor would displace upon impact would have created a crater of significant size compared to what was portrayed. It also didn't appear to have any impact to the structure of the cavern it crashed into either.
Continuity mistake: When all the students are partying outside the college, it shows the red Jeep parked up outside the college. In the next scene, it shows the "heroes" driving up to the college in the Jeep and getting out of it.
Revealing mistake: When Harry and Ira take the students to the cave to excavate the meteor, pay attention in the first wide-shot back in the cave where you can see smoke/vapor on the ground. You can see a small patch at the very bottom of the meteor where the smoke is being pumped onto the ground, likely by a concealed smoke-machine either inside of the prop meteor or just underneath the set. You can see the smoke sort-of "churning" unnaturally at the base of the meteor as it is pumped onto the ground, giving away the effect. And to avoid any corrections, yes they say that the area is being adapted by the microbial life the meteor brought to earth and developing a mini-atmosphere in the cave... but this is an unintentionally visible effect. The atmosphere/smoke/vapor wouldn't be all coming from one single tiny spot at the base of the meteor, and it wouldn't be billowing and churning like smoke being pumped from a smoke machine.
Continuity mistake: When the heroes of our film are first running away from the growing napalm induced blob to their firetruck, there are a number of shots which show nothing over their shoulders where the alien lifeforms should be undulating as its emerging from the ground.
Continuity mistake: In the scene when Wayne goes to shoot the fuzzy no-nose chimp, the glass panel behind the chimp goes from being intact to cracked and back to being intact after it's dead.
Continuity mistake: When Ira sits down in the diner scene, the utensils in front of him are lined up knife then spoon. However at the end of the scene when they go to leave, they are reversed.
Continuity mistake: During the scene when the "blob" has an arm that crashes down on top of a house, we see in the very next aerial shot that it is isolated in the desert away from any homes.
Character mistake: The acronym USGS (United States Geological Survey) is stated correctly at the beginning of the film, however, upon arriving at the military outpost, Dr Block says "United States Geological Society", not 'Survey'.
